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The 2010 CWE/SANS Top 25 Most Dangerous
Programming Errors was published today listing the most widespread issues
that lead to software vulnerabilities.
During the creation and review of the list we spent some time to see how
closely last years list matched the types of flaws we deal with at Red Hat. We
first looked at all the issues that Red Hat fixed across our entire product
portfolio in the 2009 calendar year and filtered out those that had the highest
severity. All our 2009 vulnerabilities have CVSS scores, so we filtered on
those that have a CVSS base score of 7.0 or above[1].
There were 22 vulnerabilities that matched, and we mapped each one to the
most appropriate CWE. This gives us 11 flaw types which led
to the most severe flaws affecting Red Hat in 2009:
| CWE | CWE Description | CWE/SANS top 25? | Number of Vulnerabilities |
| CWE-476 | NULL
Pointer Dereference | No (on cusp) | 6 |
| CWE-120 | Buffer
Copy without Checking Size of Input | Yes | 3 |
| CWE-129 | Improper
Validation of Array Index
| Yes | 3 |
| CWE-131 | Incorrect
Calculation of Buffer Size
| Yes | 3 |
| CWE-78 | OS
Command Injection | Yes | 1 |
| CWE-285 | Improper
Access Control (Authorization) | Yes | 1 |
| CWE-362 | Race
Condition | Yes | 1 |
| CWE-330 |
Use of Insufficiently Random Values
| No (on cusp) | 1 |
| CWE-590 | Free
of Memory not on the Heap | No | 1 |
| CWE-672 | Use
of a Resource after Expiration or Release | No (on cusp) | 1 |
| CWE-772 | Missing
Release of Resource after Effective Lifetime | No (on cusp) | 1 |
10 of the 11 CWE are mentioned in the 2010 CWE/SANS document, although 4 of them
are on "the cusp" and didn't make it into the top 25.
This quick review shows us that 2009 was the year of the kernel NULL pointer
dereference flaw, as they could allow local untrusted users to gain privileges, and
several public exploits to do just that were released. For Red Hat,
interactions with SELinux prevented them being able to be easily mitigated,
until the end of the year when
we provided updates.
Now, in 2010, the upstream Linux kernel and many vendors ship with
protections to prevent kernel NULL pointers leading to privilege escalation.
So although 2009 was the year where CWE-476 mattered to Linux administrators, it
didn't make the SANS/CWE top 25 as this flaw type should not lead to
severe issues (as long as the protections remain sufficient).
Here is a breakdown with the complete data set to show the CVSS scores and
packages affected:
| CVE | CWE | top 25? | CVSS base | Fixed in |
| CVE-2008-5182 |
CWE-362 | Yes |
7.2 | Red Hat Enterprise Linux 5 (kernel) |
| CVE-2009-0065 |
CWE-129 | Yes |
8.3 | Red Hat Enterprise Linux 4,5,MRG (kernel) |
| CVE-2009-0692 |
CWE-120 | Yes |
8.3 | Red Hat Enterprise Linux 3,4 (dhcp) |
| CVE-2009-0778 |
CWE-772 | No
(on cusp) |
7.1 | Red Hat Enterprise Linux 5 (kernel) |
| CVE-2009-0846 |
CWE-590 | No |
9.3 | Red Hat Enterprise Linux 2.1, 3 (krb5) [2] |
| CVE-2009-1185 |
CWE-131 | Yes |
7.2 | Red Hat Enterprise Linux 5 (udev) |
| CVE-2009-1385 |
CWE-129 | Yes |
7.1 | Red Hat Enterprise Linux 3,4,5,MRG (kernel) |
| CVE-2009-1439 |
CWE-131 | Yes |
7.1 | Red Hat Enterprise Linux 4,5,MRG (kernel) |
| CVE-2009-1579 |
CWE-78 | Yes |
7.5 | Red Hat Enterprise Linux 3,4,5 (squirrelmail) |
| CVE-2009-1633 |
CWE-131 | Yes |
7.1 | Red Hat Enterprise Linux 4,5,MRG (kernel) |
| CVE-2009-2406 |
CWE-120 | Yes |
7.2 | Red Hat Enterprise Linux 5 (kernel) |
| CVE-2009-2407 |
CWE-120 | Yes |
7.2 | Red Hat Enterprise Linux 5 (kernel) |
| CVE-2009-2692 |
CWE-476 | No
(on cusp) |
7.2 | Red Hat Enterprise Linux 3,4,5,MRG (kernel) |
| CVE-2009-2694 |
CWE-129 | Yes |
7.5 | Red Hat Enterprise Linux 3,4,5 (pidgin) |
| CVE-2009-2698 |
CWE-476 | No
(on cusp) |
7.2 | Red Hat Enterprise Linux 3,4,5 (kernel) |
| CVE-2009-2848 |
CWE-672 | No
(on cusp) |
7.2 | Red Hat Enterprise Linux 3,4,5,MRG (kernel) |
| CVE-2009-2908 |
CWE-476 | No
(on cusp) |
7.2 | Red Hat Enterprise Linux 5 (kernel) |
| CVE-2009-3238 |
CWE-330 | No
(on cusp) |
7.8 | Red Hat Enterprise Linux 4,5,MRG (kernel) |
| CVE-2009-3290 |
CWE-285 | Yes |
7.2 | Red Hat Enterprise Linux 5 (kvm) |
| CVE-2009-3547 |
CWE-476 | No
(on cusp) |
7.2 | Red Hat Enterprise Linux 3,4,5,MRG (kernel) |
| CVE-2009-3620 |
CWE-476 | No
(on cusp) |
7.2 | Red Hat Enterprise Linux 4,5,MRG (kernel) |
| CVE-2009-3726 |
CWE-476 | No
(on cusp) |
7.2 | Red Hat Enterprise Linux 5,MRG (kernel) |
[1] NIST NVD rate vulnerabilities as "High" severity if they have a CVSS base
score of 7.0-10.0. This ends up excluding flaws in web browsers such as Firefox
which can have a maximum CVSS base score of 6.8.
[2] Red Hat Enterprise Linux 4 and 5 were also affected by this vulnerability,
but with a lower CVSS base score of 4.3, due to the extra runtime pointer
checking.
There have been quite a few stories over the last couple of weeks
about the NULL character certificate flaw, such as this
one from The Register.
The stories center around how open source software such as Firefox was
able to produce updates to correct this issue just a few days after
the Blackhat conference, while Microsoft still hasn't fixed it and are
"investigating a possible vulnerability in Windows presented during
Black Hat".
But the actual timeline is missing from these stories.
The NULL character certificate flaw (CVE-2009-2408) was actually
disclosed by two researchers working independantly who both happened
to present the work at the same conference, Blackhat, in July this
year. Dan Kaminsky mentioned it as part of a series of PKI
flaws he disclosed. Marlinspike had found the same flaw, but was
able to demonstrate it in practice by managing to get a
trusted Certificate Authority to sign such a malicious certificate.
The flaw was no Blackhat surprise; Dan Kaminsky actually found this
issue many months ago and responsibly reported the issues to vendors
including Red Hat, Microsoft, and Mozilla. We found out about this
issue on 25th February 2009 and worked with Dan and some of the
upstream projects on these issues in advance, so we had plenty of time
to prepare updates and this is why we were able to have them ready to
release just after the disclosure.
Red Hat Enterprise Linux 5.4 was released today, just over 7 months since the
release of 5.3 in January 2009. So let's use this opportunity to take a quick
look back over the vulnerabilities and security updates we've made in that time,
specifically for Red Hat Enterprise Linux 5 Server.
Errata count
The chart below illustrates the total number of security updates issued for Red
Hat Enterprise Linux 5 Server as if you installed 5.3, up to and including the
5.4 release, broken down by severity. I've split it into two columns, one for
the packages you'd get if you did a default install, and the other if you
installed every single package (which is unlikely as it would involve a bit of
manual effort to select every one). For a given installation, the number of
package updates and vulnerabilities that affected you will depend on exactly what you
have installed or removed.

So for a default install, from release of 5.3 up to and including 5.4, we shipped 51
advisories to address 166 vulnerabilities. 8 advisories were rated critical, 18
were important, and the remaining 25 were moderate and low.
Or, for all packages, from release of 5.3 to and including 5.4, we shipped 78 advisories
to address 251 vulnerabilities. 9 advisories were rated critical, 28 were
important, and the remaining 41 were moderate and low.
Critical vulnerabilities
The 9 critical advisories were for just 3 different packages. In all the
cases below, given the nature of the flaws, ExecShield protections in RHEL5
should make exploiting these memory flaws harder.
- Seven updates to Firefox (February, March 4th, March 27th, April 21st, April 27th, June, July )
where a malicious web site could potentially run arbitrary code as the user
running Firefox.
- An update to kdelibs
(June),
where a malicious web site could potentially run arbitrary code as the
user running the Konqueror browser. kdelibs is not a default installation package.
- An update to the NSS library
(July), where
a service could present a malicious SSL certificate causing
a heap overflow which could potentially run arbitrary code as the user running
a browser such as Firefox.
Updates to correct all of these critical vulnerabilities were available via
Red Hat Network either the same day, or up to one calendar day after the issues were
public.
In fact for Red Hat Enterprise Linux 5 since release and to date, every
critical vulnerability has had an update available to address it available from
the Red Hat Network either the same day or the next calendar day after the issue
was public.
Other significant vulnerabilities
Although not in
the definition
of critical severity, also of interest during this period were several NULL
pointer dereference kernel issues. NULL pointer dereference flaws in the Linux
kernel can often be easily abused by a local unprivileged user to gain root
privileges through the mapping of low memory pages and crafting them to contain
valid malicious instructions:
- CVE-2009-2698
was public on August 24th and a working privilege escalation exploit was
published about a week later. This issue was addressed for Red Hat Enterprise
Linux 5 by
a kernel update on
August 24th.
- CVE-2009-2692
was public on August 13th and a working privilege escalation exploit was
published the same day.
This issue was addressed for Red Hat Enterprise Linux 5 by
a kernel update on
August 24th.
- CVE-2009-1897
was public on July 16th along with a working privilege escalation exploit. This issue
affected only beta versions of the Red Hat Enterprise Linux 5.4 kernel and
it was addressed prior to the release of Red Hat Enterprise Linux 5.4.
Red Hat Enterprise Linux since 5.2 has contained backported patches from the
upstream Linux kernel to add the ability to restrict unprivileged mapping of low
memory, designed to mitigate NULL pointer dereference flaws. However it was found that
this protection was not sufficient, as a system with SELinux enabled is more
permissive in allowing local users in the unconfined_t domain to map low memory
areas even if the mmap_min_addr restriction is enabled. This is
CVE-2009-2695
and will be addressed in a future kernel update.
Mitigations
Red Hat Enterprise Linux 5 shipped with a number of security technologies
designed to make it harder to exploit vulnerabilities and in some cases block
exploits for certain flaw types completely. From 5.3 to 5.4 there
were three flaws blocked that would otherwise have required critical updates:
- CVE-2009-0692,
a stack buffer overflow flaw in dhclient.
FORTIFY_SOURCE protection detects the overflow and causes dhclient to exit with
no security consequence. No security update for users of Red Hat Enterprise
Linux 5 was needed.
-
CVE-2009-1252
a buffer overflow flaw in NTP caught by FORTIFY_SOURCE.
We issued an
update as a remote attacker could still cause a denial of service.
- CVE-2009-0846,
a uninitialized pointer free in krb5. glibc provides a hardened malloc/free
implementation which mitigates the exploitability of this flaw, however we
issued an update as a remote attacker could still cause a denial
of service.
Previous updates
To compare these statistics with previous update releases we need to take into
account that the time between each update is different. So looking at a default
installation and calculating the number of advisories per month gives the results
illustrated by the following chart:

This data is interesting to get a feel for the risk of running Enterprise Linux
5 Server, but isn't really useful for comparisons with other versions,
distributions, or operating systems -- for example, a default install of Red Hat
Enterprise Linux 4AS did not include Firefox, but 5 Server does. You can use
our public security
measurement data and tools, and run your own custom metrics for any given
Red Hat product, package set, timescales, and severity range of interest.
See also:
5.2 to 5.3,
5.1 to 5.2, and
5.0 to 5.1
risk reports.
From time to time I publish metrics on vulnerabilities that affect
Red Hat Enterprise Linux. One of the more interesting metrics looks at
how far in advance we know about the vulnerabilities we fix, and from where
we get that information. This post is abstracted from the upcoming "4 years of Enterprise Linux 4"
risk report
For every fixed vulnerability across every package and every
severity in Enterprise Linux 4 AS in the first 4 years of its life, we
determined if the flaw was something we knew about a day or more in advance of
it being publicly disclosed, and how we found out about the flaw.

For vulnerabilities which are already public when we first hear about them
we still track the source as it's a useful internal indicator on where the
security
response team
should focus their efforts.

So from this data, Red Hat knew about 51% of the security vulnerabilities that
we fixed at least a day in advance of them being publicly disclosed. For those
issues, the average notice was 21 calendar days, although the median
was much lower, with half the private issues having advance notice of 9
days or less.

Red Hat Enterprise Linux 5.3 was released today, around 8 months since the
release of 5.2 in May 2008. So let's use this opportunity to take a quick
look back over the vulnerabilities and security updates we've made in that time,
specifically for Red Hat Enterprise Linux 5 Server.
The chart below shows the total number of security updates issued for Red Hat
Enterprise Linux 5 Server as if you installed 5.2, up to and including the 5.3
release, broken down by severity. I've split it into two columns, one for the
packages you'd get if you did a default install, and the other if you installed
every single package (which is unlikely as it would involve a bit of manual
effort to select every one). So, for a given installation, the number of
packages and vulnerabilities will probably be somewhere between the two.
So for a default install, from release of 5.2 up to and including 5.3, we shipped 45
advisories to address 127 vulnerabilities. 7 advisories were rated critical, 21
were important, and the remaining 17 were moderate and low.
For all packages, from release of 5.2 to and including 5.3, we shipped 61 advisories
to address 181 vulnerabilities. 7 advisories were rated critical, 28 were
important, and the remaining 26 were moderate and low.
The 7 critical advisories were for just 3 different packages:
- Five updates to Firefox (July, July, September, November, December)
where a malicious web site could potentially run arbitrary code as the user
running Firefox. Given the nature of the flaws, ExecShield protections in RHEL5
should make exploiting these memory flaws harder.
- An update to Samba
(May), where a
remote attacker who can connect and send a print request to a Samba server could
cause a heap overflow. The Red Hat Security Response Team believes it would
be hard to remotely exploit this issue to execute arbitrary code due to the
default enabled SELinux targeted policy and the default enabled SELinux memory
protection tests. We are not aware of any public exploit for this issue.
- An update to OpenSSH
(August),
provided to mitigate an intrusion into certain Red Hat computer systems. The
attacker was able to sign a small number of tampered packages but they were not
distributed on the Red Hat Network. We classified this update as critical to ensure
any tampered packages would be replaced with official packages.
Although not of critical severity, also of interest during this period
were the spoofing attacks on DNS servers. We provided an update to BIND
(July) adding
source port randomization to help mitigate these attacks.
Updates to correct all of these critical vulnerabilities (as well as migitate
the BIND issue) were available via Red Hat
Network either the same day, or one calendar day after the issues were
public.
In fact for Red Hat Enterprise Linux 5 since release and to date, every
critical vulnerability has had an update available to address it available from
the Red Hat Network either the same day or the next calendar day after the issue
was public.
To compare this with the last updates we need to take into account that the
time between each update is different. So looking at a default installation
and calculating the number of advisories per month gives the following
chart:
Red Hat Enterprise Linux 5 shipped with a number of security technologies
designed to make it harder to exploit vulnerabilities and in some cases block
exploits for certain flaw types completely. For 5.2 to 5.3 there
were two flaws blocked that would otherwise have required updates:
- A double-free
flaw in unzip.
The glibc
pointer checking
limited the exploitability of
this issue to just a crash of unzip, a client application, which does not
have security implications. No security update was needed.
- Two format
string flaws in c++filt. The format string protection
caused these issues to have no security implications. No security
update was needed.
This data is interesting to get a feel for the risk of running Enterprise Linux
5 Server, but isn't really useful for comparisons with other versions,
distributions, or operating systems -- for example, a default install of Red Hat
Enterprise Linux 4AS did not include Firefox, but 5 Server does. You can use
our public security
measurement data and tools, and run your own custom metrics for any given
Red Hat product, package set, timescales, and severity range of interest.
See also:5.1 to 5.2
risk report
Secunia collect some very interesting information about the patch
state of Windows systems. Their results from 20,000 machines published
yesterday were that over 98% of PCs were
insecure, having at least one out-of-date application installed.
Actually this isn't surprising and is exactly what I'd expect;
it's all down to third party applications.
Let's say you're browsing the web. It's more than likely that at
some point you'll want to view some PDF files, watch some Flash
content, or play a Java game. Those tasks are all dealt with by third
party applications, although to the end user it's all part of the
browser experience. Since your system is only as secure as its
weakest link, you need to manage security updates for those third
party applications just as carefully as you manage security updates
for the rest of your system. That's why Adobe Reader, Java, Flash,
and all the myriad of other applications you've installed in order to
make your system useful have their own update mechanisms. Some
applications on Windows will 'phone home' when they are run and check
to see if they need to be updated, others deploy services that sit in
the background looking for updates from time to time, others even
check every time your system starts. Many don't get automated updates
at all.
How do you deal with all that risk? I believe it's possible by
providing an OS distribution which includes all the bits you'll
likely need to make a useful computing environment, thereby taking
away that update uncertainty. Red Hat ship several PDF viewers in our
distributions for example, but we also ship (in an Extras channel)
Adobe Reader. Our Security Response Team are monitoring for security
issues in everything we ship, all the third party applications,
and providing a single point of contact, a single
notification system, and a single way to get the updates.
If Microsoft knew that say 25% of all their users installed
Firefox, wouldn't they be better bundling it and providing their
centralised automated updates for it, to reduce their customers
overall risk? They do already bundle some third party applications, although it's
been with mixed success as we found 3 years ago when they
didn't
provide security fixes for bundled Flash (ZDNet
coverage).
This is, in part, why you've not seen me respond recently to the
Vista security reports which compare vulnerability counts. In these
reports they use a cut-down minimal Red Hat Enterprise Linux
installation in order to make it look more like Windows for the
comparisons. But this is completely backwards -- the fact that we're
including and fixing the flaws using a common process in so much
third party software is actually helping reduce the risk and protect
real customers. For example we could easily cut our vulnerability
count by shipping only one PDF viewer instead of four. But if we know
that these other viewers are going to get installed by the customer
anyway all we've done is to hide the vulnerability count elsewhere,
and you've made the customers overall risk increase.
So it may seem counter-intuitive but we should ship as much third
party applications (that we know people use) as we can, because a
single managed security update and notification process will decrease
a users overall risk. The fewer third party applications that users
have to get from elsewhere and install and manage for themselves the better
in my opinion.
Red Hat Enterprise Linux 5.2 was released last week, around 6 months since the
release of 5.1 in November 2007. So let's use this opportunity to take a quick
look back over the vulnerabilities and security updates we've made in that time,
specifically for Red Hat Enterprise Linux 5 Server.
The graph below shows the total number of security updates issued for Red Hat
Enterprise Linux 5 Server starting at 5.1 up to and including the 5.2 release,
broken down by severity. I've split it into two columns, one for the packages
you'd get if you did a default install, and the other if you installed every
single package (which is unlikely as it would involve a bit of manual effort
to select every one). So, for a given installation, the number
of packages and vulnerabilities will probably be somewhere between the two.
So for a default install, from release of 5.1 up to and including 5.2, we shipped 46
updates to address 119 vulnerabilities. 8 advisories were rated critical, 24
were important, and the remaining 14 were moderate and low.
For all packages, from release of 5.1 to and including 5.2, we shipped 62 updates
to address 179 vulnerabilities. 9 advisories were rated critical, 29 were
important, and the remaining 24 were moderate and low.
The nine critical updates were in five different packages:
- Four updates to Firefox (November, February, March, April)
where a malicious web site could potentially run arbitrary code as the
user running Firefox. Given the nature of the flaws, ExecShield
protections in RHEL5 should make exploiting these memory flaws
harder.
- An update to the GnuTLS library (May), where
a remote attacker who can connect to a server making use of GnuTLS could
cause a buffer overflow. In Red Hat Enterprise Linux 5, the CUPS print
server uses GnuTLS.
- An update to MIT Kerberos (March),
where a remote attacker who can conect to the krb5kdc or kadmind
services could cause a buffer overflow.
- An update to OpenPegasus
(January), where
a remote attacker who can connect to OpenPegasus could cause a buffer overflow.
The Red Hat Security Response Team believes that it would be hard to remotely
exploit this issue to execute arbitrary code, due to the default SELinux
targeted policy, and the default SELinux memory protection tests.
- Two updates to Samba (November, December) where
a remote attacker who can connect to the Samba port could cause buffer
overflows. In addition to
ExecShield making this harder to exploit, the impact of any sucessful
exploit would be reduced as Samba is constrained by an SELinux targeted
policy (enabled by default).
Updates to correct all of these critical issues were available via Red Hat
Network either the same day, or one calendar day after the issues were public.
To get a better idea of risk we need to look not only at the vulnerabilities but
also the exploits written for those vulnerabilities.
A proof of concept exploit exists publicly for one of the
Samba flaws,
CVE-2007-6015,
but we are not aware of public exploits for any other of those critical
vulnerabilities. Also of high risk was an important "zero-day" exploit affecting the Linux
kernel where a local unprivileged user could gain root privileges.
Red Hat Enterprise Linux 5.1 was affected and
a fix was
available two calendar days after public disclosure.
Red Hat Enterprise Linux 5 shipped with a number of security technologies
designed to make it harder to exploit vulnerabilities and in some cases block
exploits for certain flaw types completely. For the period of this study there
were two flaws blocked that would otherwise have required updates:
- A double-free flaw in CUPS. The glibc pointer checking limited the
exploitability of this issue to just a crash of CUPS and not the ability to
execute arbitrary code. code execution. We
still issued an
update, as a remote attacker could trigger this flaw and cause CUPS to
crash.
- An uninitialized pointer free flaw in unzip, caught by the glibc pointer
checking. As exploitation of this flaw results in just
a crash of a
user application, no updates were needed.
This data is interesting to get a feel for the risk of running Enterprise Linux
5 Server, but isn't really useful for comparisons with other versions or
distributions -- for example, a default install of Red Hat Enterprise 4AS did
not include Firefox. You can get the results I presented above for yourself by
using our public
security measurement data and tools, and run your own custom metrics for any
given Red Hat product, package set, timescales, and severities.
See also 5.0 to 5.1 risk report
It sometimes seems like the Security Response Team at Red Hat are
pushing security updates every day, but actually a default
installation of Enterprise Linux 4 AS was vulnerable to only 7
critical security issues in the first three years since release. But to
get a picture of the risk you need to do more than count
vulnerabilities.
My full
risk report was published yesterday in Red Hat Magazine and
reveals the state of security since the release of Red Hat Enterprise
Linux 4 including metrics, key vulnerabilities, and the most common
ways users were affected by security issues.
"Red Hat knew about 49% of the security
vulnerabilities that we fixed in advance of them being publicly
disclosed. For those issues, the average notice was 21 calendar days,
although the median was much lower, with half the private issues
having advance notice of 8 days or less."
Secunia released a security summary report for 2007 and surprisingly
gave a count for Red Hat for the year at over 600 vulnerabilities. I
had no idea how they got to this number, it certainly doesn't match
our own publicly available metrics at
http://www.redhat.com/security/data/metrics
Using our public tool, for every Red Hat product and service, for 2007
we issued 306 advisories to fix 404 vulnerabilities. Of those 404
vulnerabilities 41 were critical (on the scale used by Microsoft and
Red Hat).
Most people are not going to be using every Red Hat product, so taking
just Enterprise Linux product you find 348 vulnerabilities, of which 27
were critical. A given user is going to only be vulnerable to the issues that affect
the products and packages they have installed. Using the scripts on
our pages you can figure it out for your own circumstances. But as an
example, the default installation of Red Hat Enterprise Linux 4 AS had
172 vulnerabilities of which 4 were critical.
The Secunia report does actually make it clear you can't use their
vulnerability count as a method of comparing platforms, in part due to the
differences in methodology of the vendors, but I'm sure this won't stop
some press from jumping to conclusions if they don't read the actual report.
I've asked Secunia how they got to their number of vulnerabilities, but in the
meantime, a raw count of vulnerabilities is only a small part of the
overall risk exposure in using a product. I've got some more reports that go
into this in more detail for two years of Enterprise Linux 4 and Enterprise Linux
5.0 to 5.1.
Update: Coverage of this: ZDNet
Update: Secunia told me that they treat each advisory separately; so for example
yesterday we issued updates for some moderate severity issues in
the Apache Web server, but we did separate advisories for each affected
product: Red Hat Enterprise Linux 2.1, 3, 4, 5, Red Hat Application Stack v1, v2.
So in this case the same Apache vulnerability would be counted 6 times.
Red Hat Enterprise Linux 5.1 was released today, around 8 months since the
release of 5.0 in March 2007. So let's use this opportunity to take a quick
look back over the vulnerabilities and security updates we've made in that time,
specifically for Red Hat Enterprise Linux 5 Server.
The graph below shows the total number of security updates issued for Red Hat
Enterprise Linux 5 Server up to and including the 5.1 release,
broken down by severity. I've split it into two columns, one for the packages
you'd get if you did a default install, and the other if you installed every
single package (which is unlikely as it would involve a bit of manual effort
to select every one). So, for a given installation, the number
of packages and vulnerabilities will be somewhere between the two extremes.
So for all packages, from release up to and including 5.1, we shipped 94 updates
to address 218 vulnerabilities. 7 advisories were rated critical, 36 were
important, and the remaining 51 were moderate and low.
For a default install, from release up to and including 5.1, we shipped 60
updates to address 135 vulnerabilities. 7 advisories were rated critical, 26
were important, and the remaining 27 were moderate and low.
- These figures include ten updates we released on the day we shipped 5.0. This was
because we froze package updates some months before releasing the product. Only
one of those updates was rated critical, an update to Firefox.
- The six other critical updates were:
- Three more updates to Firefox (May, July, October)
where a malicious web site could potentially run arbitrary code as the
user running Firefox. Given the nature of the flaws, ExecShield
protections in RHEL5 should make exploiting these memory flaws
harder.
- An update to the Kerberos telnet deamon (April)
A remote attacker who can access the telnet
port of a target machine could log in as root without requiring a
password. None of the standard protection mechanisms help prevent
exploitation of this issue, however the krb5 telnet daemon is not
enabled by default in Enterprise Linux 5 and the default firewall rules
block remote access to the telnet port. This flaw did not affect the
more common telnet daemon distributed in the telnet-server
package.
- An update to Samba (May) where
a remote attacker could cause a heap overflow. In addition to
ExecShield making this harder to exploit, the impact of any sucessful
exploit would be reduced as Samba is constrained by an SELinux targeted
policy (enabled by default).
- An update to the PCRE library (November). This
was labelled critical because the Konqueror web browser uses PCRE to handle
regular expressions in JavaScript, and therefore a user browsing a malicious
site in Konqueror could trigger this issue. (Konqueror is not part of
a default install, but I've left this issue as critical in the results).
- Updates to correct all of these critical issues were available via Red Hat
Network within a day of the issues being public.
Red Hat Enterprise Linux 5 shipped with a number of security technologies
designed to make it harder to exploit vulnerabilities and in some cases block
exploits for certain flaw types completely. For the period of this study there
were two flaws blocked that would otherwise have required critical updates:
- A stack buffer overflow flaw in the RPC library in Kerberos.
This flaw was blocked by FORTIFY_SOURCE which removed the possibility of remote
code execution. We still issued an update,
as a remote attacker could trigger this flaw and cause Kerberos to crash.
- Another flaw in Kerberos, this time due to the free of an invalid
pointer. This flaw was blocked by glibc, although a remote attacker could still
cause
a crash, so we
issued an update.
This data is interesting to get a feel for the risk of running Enterprise Linux
5 Server, but isn't really useful for comparisons with other versions or
distributions -- for example, a default install of Red Hat Enterprise 4AS did
not include Firefox. You can get the results I presented above for yourself by
using our public security
measurement data and tools, and run your own metrics for any given Red Hat
product, package set, timescales, and severities.
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