Vulnerability Scanners and Red Hat Enterprise Linux

I’m capturing this information here because I find that I deliver some version of this rant roughly once every six months, and it would be really nice to not have to keep doing so.


I have manually verified that servers are still highly vulnerable due to out of date versions of Apache, PHP, and cURL. The latest security updates are available for these products, and the attached report shows from where the updates can be downloaded.

Can we patch these servers before August ? I hope that we can achieve this, so that our customer can meet their August 1st deadline.

so, the cURL vulnerability is within our capacity to patch; as your document shows, Red Hat released an updated package on 6/25/2013 that patches this vulnerability. this package will be synced into our next patch snapshot, which will be prepared shortly before the end of July; we can certainly do our best to make sure that this server is patched as quickly as possible after the next patch snapshot is available, provided the customer is able to cooperate.

as for the other vulnerabilities, “upgrad[ing] Apache and PHP to the latest stable version” is simply not a solution that makes sense within the context of an enterprise Linux distribution like RHEL. please, if you have not already done so, read the following document:

Red Hat, as a matter of policy, does not change the version number of its supported packages during a major release (and the lifecycle of a major release is on the order of seven years), except under exceptional circumstances. the server in question runs RHEL5, which means that the packaged version of Apache is 2.2.3. however, that version of Apache is NOT a vanilla build of Apache 2.2.3 as shipped by the Apache Project on July 28, 2006. instead, it contains backported fixes for security vulnerabilities discovered since then; therefore it is NOT necessarily vulnerable to exploits that would successfully attack a vanilla Apache 2.2.3.

the same is true for PHP, and for all the other packages that make up a RHEL distribution. therefore it doesn’t make any sense to make assumptions about a RHEL system’s vulnerability based on version number inspection alone; it is necessary to look at the release number as well. for example, consider plugin 42052 from the vulnerability report attached to the ticket; it checks for vulnerability to CVE-2009-2699, CVE-2009-3094, and CVE-2009-3095. let’s look at those in detail:

CVE-2009-2699 appears in Red Hat’s CVE database:

however, as the documentation shows, this vulnerability only affects Solaris systems, and in addition only affects versions of APR (Apache Portable Runtime) that are older than the version shipped with RHEL5, so this vulnerability is irrelevant to this server.

CVE-2009-3094 also appears in Red Hat’s CVE database:

Red Hat published a series of errata with patches for this vulnerability; the appropriate one for this server is here:

this erratum tells us that to patch this vulnerability, we need to install httpd-2.2.13-2.el5s2 or later. let’s take a look at the version installed on this server:

  [root@fdd-web ~]# rpm -q httpd

hey, that’s the version we need! this means that even though the Apache daemon reports its version as “2.2.13”, it is NOT VULNERABLE to CVE-2009-3094.

CVE-2009-3095 also appears in Red Hat’s CVE database:

it also has errata associated with it, and its patch is included in the same version of the httpd package mentioned above, which is installed on the server in question. that means, again, that this server is NOT VULNERABLE to CVE-2009-3095.

so, what does all this mean? this means that plugin 42052 shows a FALSE POSITIVE when run against the server in question. as best i can tell, the server is not currently vulnerable to any of the CVEs referenced by that plugin, and the security scanner doesn’t have enough information to realize that. i suspect that the same will be the case for many (but maybe not all) of the other plugins in the vulnerability report.

i am confident that these are only some of the false positives contained in the vulnerability report. i haven’t even gotten to the many disadvantages of blindly installing custom-compiled Apache and PHP binaries to satisfy vulnerability scanners:

  1. we lose any ability to get support from Red Hat concerning any issue we may have with those binaries in the future

  2. we lose any optimizations and distribution-specific features that Red Hat includes in its own packages (these packages are not just about security fixes)

  3. we lose the ability to deploy any other packages from the RHEL distribution, or from EPEL, or from any other RHEL-compatible package repository, that depend on Apache or PHP binaries

and we lose all of these things just to satisfy a false positive.