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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
- 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
- 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
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
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.
Created: 07 Nov 2007
Tagged as: metrics, red hat, security
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Hi! I'm Mark Cox. This blog gives my
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