Red Hat Enterprise Linux 5.8 was released today (February 2012), seven months since the release of 5.7 in July 2011. So let's use this opportunity to take a quick look back over the vulnerabilities and security updates made in that time, specifically for Red Hat Enterprise Linux 5 Server.
Red Hat Enterprise Linux 5 is coming up to its fifth year since release, and is supported for another five years, until 2017.
The chart below illustrates the total number of security updates issued for Red Hat Enterprise Linux 5 Server if you had installed 5.7, up to and including the 5.8 release, broken down by severity. It's split 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 quite 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 packages you have installed or removed.
So, for a default install, from release of 5.7 up to and including 5.8, we shipped 42 advisories to address 118 vulnerabilities. 4 advisories were rated critical, 13 were important, and the remaining 25 were moderate and low.
Or, for all packages, from release of 5.7 up to and including 5.8, we shipped 71 advisories to address 177 vulnerabilities. 7 advisories were rated critical, 16 were important, and the remaining 48 were moderate and low.
The 7 critical advisories addressed 20 critical vulnerabilities across 4 different packages:
An update to OpenJDK 6 Java Runtime Environment, (October 2011) where a web site hosting a malicious Java applet could potentially run arbitrary code as the user.
An update to the MIT krb5 telnet daemon (December 2011) where a remote attacker who can access the telnet port of a target machine could use this flaw to execute arbitrary code as root. Note that the krb5 telnet daemon is not installed or enabled by default, and the default firewall rules block remote access to the telnet port. This flaw did not affect the more commonly used telnet daemon distributed in the telnet-server package.
Updates to PHP and PHP 5.3 (February 2012) where a remote attacker could send a specially-crafted HTTP request to cause the PHP interpreter to crash or, possibly, execute arbitrary code. This flaw was caused by the fix for CVE-2011-4885.
Updates to correct 19 out of the 20 critical vulnerabilities were available via Red Hat Network either the same day or the next calendar day after the issues were public. The update to krb5 took 2 calendar days because it was public on Christmas day.
Overall, for Red Hat Enterprise Linux 5 since release until 5.8, 98% of critical vulnerabilities have had an update available to address them 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 a couple of remote denial of service flaws that were easily exploitable:
Previous update releases
To compare these statistics with previous update releases we need to take into account that the time between each update release is different. So looking at a default installation and calculating the number of advisories per month gives 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 major 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.