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mark :: blog :: cvss
We now have an official Red Hat Security Blog, and you'll find all my future
reports and discussions about security metrics there. In the meantime
here are a few already published articles:
A few weeks ago the 2011 update to
the CWE/SANS Top 25 Most Dangerous
Software Errors was published. As part of our contribution to this
update we analysed the most severe vulnerabilities that affected Red Hat
since the last update and mapped each one to the appropriate Common
Weakness Enumeration (CWE) type.
The table below lists all vulnerabilities which have a CVSS score of 7
or more ('high'), that we fixed in any product during calendar year 2010.
Most common CWE were: - Buffer Copy without Checking
Size of Input
(CWE-120): 8 vulnerabilities.
-
Race Condition
(CWE-362): 5 vulnerabilities.
| CVE | CWE | 2011 top 25? | CVSS base score | Fixed in |
|---|
|
CVE-2007-4567
| CWE-476 | no
| 7.8
| Red Hat Enterprise Linux 5 (kernel)
|
|
CVE-2009-0778
| CWE-770 | no
| 7.1
| Red Hat Enterprise Linux 5 (kernel)
|
|
CVE-2009-1385
| CWE-191 | no
| 7.1
| Red Hat Enterprise Linux 5 (kernel)
|
|
CVE-2009-3080
| CWE-129 | no
| 7.2
| Red Hat Enterprise Linux 3, 4, 5, MRG (kernel)
|
|
CVE-2009-3245
| CWE-252 | no
| 7.6
| Red Hat Enterprise Linux 3, 4, 5 (openssl)
|
|
CVE-2009-3726
| CWE-476 | no
| 7.2
| Red Hat Enterprise Linux 4, 5, MRG (kernel)
|
|
CVE-2009-4005
| CWE-127 | no
| 7.1
| Red Hat Enterprise Linux 4 (kernel)
|
|
CVE-2009-4027
| CWE-362 | no
| 7.8
| Red Hat Enterprise Linux 5 (kernel)
|
|
CVE-2009-4141
| CWE-416 | no
| 7.2
| Red Hat Enterprise Linux 5, MRG (kernel)
|
|
CVE-2009-4212
| CWE-191 | no
| 10.0
| Red Hat Enterprise Linux 3, 4, 5 (krb5)
|
|
CVE-2009-4272
| CWE-764 | no
| 7.8
| Red Hat Enterprise Linux 5 (kernel)
|
|
CVE-2009-4273
| CWE-78 | yes
| 7.9
| Red Hat Enterprise Linux 5 (systemtap)
|
|
CVE-2009-4537
| CWE-120 | yes
| 7.1
| Red Hat Enterprise Linux 4, 5, MRG (kernel)
|
|
CVE-2009-4895
| CWE-362 | no
| 7.2
| Red Hat Enterprise MRG (kernel)
|
|
CVE-2010-0008
| CWE-606 | no
| 7.8
| Red Hat Enterprise Linux 4, 5 (kernel)
|
|
CVE-2010-0291
| CWE-822 | no
| 7.2
| Red Hat Enterprise Linux 5 (kernel)
|
|
CVE-2010-0738
| CWE-424 | no
| 7.5
| JBoss Enterprise Application Platform 4.2, 4.3
|
|
CVE-2010-0741
| CWE-20 | no
| 7.1
| Red Hat Enterprise Linux 5 (kvm)
|
|
CVE-2010-1084
| CWE-120 | yes
| 7.2
| Red Hat Enterprise Linux 5 (kernel)
|
|
CVE-2010-1086
| CWE-20 | no
| 7.8
| Red Hat Enterprise Linux 4, 5 (kernel)
|
|
CVE-2010-1087
| CWE-362 | no
| 7.2
| Red Hat Enterprise Linux 5 (kernel)
|
|
CVE-2010-1166
| CWE-823 | no
| 7.6
| Red Hat Enterprise Linux 5 (xorg-x11-server)
|
|
CVE-2010-1173
| CWE-120 * | yes
| 7.1
| Red Hat Enterprise Linux 4, 5 (kernel)
|
|
CVE-2010-1188
| CWE-416 | no
| 7.8
| Red Hat Enterprise Linux 3, 4, 5 (kernel)
|
|
CVE-2010-1436
| CWE-120 | yes
| 7.2
| Red Hat Enterprise Linux 5 (kernel)
|
|
CVE-2010-1437
| CWE-362 | no
| 7.2
| Red Hat Enterprise Linux 4, 5 (kernel)
|
|
CVE-2010-2063
| CWE-823 | no
| 7.5
| Red Hat Enterprise Linux 3, 4, 5 (samba)
|
|
CVE-2010-2235
| CWE-77 | no
| 7.1
| Red Hat Network Satellite Server 5.3 (cobbler)
|
|
CVE-2010-2240
| CWE-788 | no
| 7.2
| Red Hat Enterprise Linux 3, 4, 5, MRG (kernel)
|
|
CVE-2010-2248
| CWE-682 | no
| 7.1
| Red Hat Enterprise Linux 4, 5 (kernel)
|
|
CVE-2010-2492
| CWE-805 | no
| 7.2
| Red Hat Enterprise Linux 5, 6 (kernel)
|
|
CVE-2010-2521
| CWE-805 | no
| 8.3
| Red Hat Enterprise Linux 4, 5, MRG (kernel)
|
|
CVE-2010-2798
| CWE-476 | no
| 7.2
| Red Hat Enterprise Linux 5 (kernel)
|
|
CVE-2010-2962
| CWE-823 | no
| 7.2
| Red Hat Enterprise Linux 6, MRG (kernel)
|
|
CVE-2010-3069
| CWE-129 | no
| 8.3
| Red Hat Enterprise Linux 3, 4, 5, 6 (samba)
|
|
CVE-2010-3081
| CWE-131 | yes
| 7.2
| Red Hat Enterprise Linux 3, 4, 5, 6, MRG (kernel)
|
|
CVE-2010-3084
| CWE-120 | yes
| 7.2
| Red Hat Enterprise Linux 6 (kernel)
|
|
CVE-2010-3301
| CWE-129 | no
| 7.2
| Red Hat Enterprise Linux 6 (kernel)
|
|
CVE-2010-3302
| CWE-120 | yes
| 7.1
| Red Hat Enterprise Linux 6 (openswan)
|
|
CVE-2010-3308
| CWE-120 | yes
| 7.1
| Red Hat Enterprise Linux 6 (openswan)
|
|
CVE-2010-3432
| CWE-805 * | no
| 7.8
| Red Hat Enterprise Linux 4, 5, 6, MRG (kernel)
|
|
CVE-2010-3705
| CWE-788 | no
| 8.3
| Red Hat Enterprise Linux 6, MRG (kernel)
|
|
CVE-2010-3708
| CWE-77 | no
| 7.5
| JBoss Enterprise Application Platform 4.3, SOA Platform 4.2
|
|
CVE-2010-3752
| CWE-78 | yes
| 7.1
| Red Hat Enterprise Linux 6 (openswan)
|
|
CVE-2010-3753
| CWE-78 | yes
| 7.1
| Red Hat Enterprise Linux 6 (openswan)
|
|
CVE-2010-3847
| CWE-426 | no
| 7.2
| Red Hat Enterprise Linux 5, 6 (glibc)
|
|
CVE-2010-3856
| CWE-426 | no
| 7.2
| Red Hat Enterprise Linux 5, 6 (glibc)
|
|
CVE-2010-3864
| CWE-362 | no
| 7.6
| Red Hat Enterprise Linux 6 (openssl)
|
|
CVE-2010-3904
| CWE-822 | no
| 7.2
| Red Hat Enterprise Linux 5, 6 (kernel)
|
|
CVE-2010-4170
| CWE-88 | no
| 7.2
| Red Hat Enterprise Linux 4, 5, 6 (systemtap)
|
|
CVE-2010-4179
| CWE-862 | yes
| 7.5
| Red Hat Enterprise MRG (cumin)
|
|
CVE-2010-4344
| CWE-120 | yes
| 7.5
| Red Hat Enterprise Linux 4, 5 (exim)
|
* - in both these cases the outcome is not a buffer overflow as the possible
overflow is detected and instead converted into an abort (DoS)
See also our 2010 analysis
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.
Back in
August I found that many of the Common Vulnerability Scoring
System (CVSS) scores that the National Vulnerability Database (NVD)
assigned to vulnerabilities affecting open source software were incorrect.
Since then I've been sending in corrections on a monthly basis,
taking into account the worst possible score across all affected
platforms (and not how Red Hat products were affected specifically).
For the five months May to September 2007 I looked at 178
vulnerabilities (across all Red Hat products and services). Only 80
were accurate. Corrections were submitted to NVD and they fixed the
incorrect CVSS scores on the remaining 98 vulnerabilities. 
So, before the corrections, there were 65 issues rated "High" out
of 178. After the corrections there are actually only 17 rated
"High". Fortunately the number of corrections needed each month
seems to be decreasing, but we'll continue to send in corrections
every month. Even with the corrections, the
severity rating for a given vulnerability may well vary for the
version each vendor ships; so you need to be careful if you are basing
your risk assesments soley on the accuracy of third-party severity ratings.
The National Vulnerability Database (NVD)
assign a severity rating to every vulnerability; "High", "Medium", or "Low".
The rating is determined by ranges of CVSS (Common Vulnerability Scoring System)
v2 scores. I've not been a big fan of CVSS: I don't think it works particularly
well when applied to software that is shipped by multiple vendors, or
for open source software and libraries that don't know all the possible
use-cases of their software.
Even though I'm not a fan, NVD publish a CVSS score for every issue,
security companies are using those scores in their vulnerability feeds to
customers, and people are using them for metrics. So it's important that
these scores are accurate.
I decided to take a look at how accurate the CVSS scores were, so for every
vulnerability we fixed in any Red Hat product for June 2007 examined the CVSS
score given by NVD. For each one figuring out if the CVSS base metrics were
correct, and where they were not submitting the correction back to NVD. This
analysis of the vulnerabilities was based on their possible worst-case threat to
all platforms (I didn't adjust the CVSS scores for how the issues affected Red
Hat products specifically).
There were 39 total vulnerabilities for which unfortunately only 8 scores were
accurate. I submitted corrections to NVD and they fixed the CVSS scores on the
remaining 31 vulnerabilities.
20 vulnerabilities ended up moving down in ranking, 6 vulnerabilities
moved up, and 5 stayed the same (although the CVSS score changed).
Before the corrections there were 14 issues rated "High" out of 39,
after the corrections there are just 3 rated "High".
Those corrections are now live in the NVD, and I really appreciate how quick the
folks behind NVD were at checking and making the changes. I've submitted to
them corrections for a couple more months too, and I'll write about those when
there complete. Unfortunately it does take a lot of time to investigate each
issue and do the corrections, so it will limit how far back into 2007
we can correct.
The National Vulnerability Database provides a public severity rating
for all CVE named vulnerabilities, "Low" "Medium" and "High",
which they generate automatically based on the CVSS score their
analysts calculate for each issue. I've been interested for some time to see
how well those map to the severity ratings that Red Hat give to
issues. We use the same ratings
and methodology as Microsoft and others use, assigning "Critical"
for things that have the ability to be remotely exploited automatically
through "Important", "Moderate", to "Low".
Given a thundery Sunday afternoon I took the last 12 months of all possible
vulnerabilities affecting Red Hat Enterprise Linux 4 (from 126 advisories across
all components) from my metrics page and compared to NVD using their provided XML
data files. The result broke down like this:
| Red Hat |
| 13% Crit |
24% Important |
39% Moderate |
24% Low |
| | NVD |
| 30% High |
20% Moderate |
|
50% Low |
|
So that looked okay on the surface; but the diagram above implies that
all the issues Red Hat rated as Critical got mapped in NVD to High. But
that's not actually the case, and when you
look at the breakdown you get this result: (in number of vulnerabilities)
That shows nearly half of the issues that NVD rated as High actually only
affected Red Hat with Moderate or Low severity. Given our policy is to fix the
things that are Critical and Important the fastest (and we have a pretty impressive record
for fixing critical issues), it's no wonder that recent vulnerability studies
that use the NVD mapping when analysing Red Hat vulnerabilities have some
significant data errors.
I wasn't actually surprised that there are so many differences: my
hypothesis is that many of the errors are due to the nature of how
vulnerabilities affect open source
software. Take for example the Apache HTTP server. Lots of companies ship
Apache in their products, but all ship different versions with different
defaults on different operating systems for different architecture compiled with
different compilers using different compiler options. Many Apache
vulnerabilities over the years have affected different platforms in
significantly different
ways. We've seen an Apache vulnerability that leads to arbitrary code execution
on older FreeBSD, that causes a denial of service on Windows, but that was
unexploitable on Linux for example. But it has a single CVE identifier.
So if you're using a version of the Apache web server you
got with your Red Hat Enterprise Linux distribution then you need to
rely on Red Hat to tell you how the issue affects the version they
gave you -- in the same way you rely on them to give you an update
to correct the issue.
I did also spot a few instances where the CVSS score for a given vulnerability
was not correctly coded. CVSS version 2 was released last week and once NVD is
based on the new version I'll redo this analysis and spend more time submitting
corrections to any obvious mistakes.
But in summary: for multi-vendor software the severity rating for a given
vulnerability may very well be different for each vendors version. This is a
level of detail that vulnerability databases such as NVD don't currently
capture; so you need to be careful if you are relying on the accuracy of
third party severity ratings.
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Hi! I'm Mark Cox. This blog gives my
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