Oracle Releases Out-of-Cycle Patch as Fix for "Apache Killer"

In a recent security alert, Oracle Corporation advised potentially affected customers to patch their software against vulnerabilities that can result in effective denial-of-service attacks against web servers.  The security alert is identified as CVE-2011-3192.

According to the Oracle, the affected systems include the following:

• Oracle Fusion Middleware 11g Release 1, versions:
  • 11.1.1.3.0
  • 11.1.1.4.0
  • 11.1.1.5.0
• Oracle Application Server 10g Release 3, version 10.1.3.5.0
• Oracle Application Server 10g Release 2, version 10.1.2.3.0

The latter two are only considered affected when Oracle HTTP Server 10g based on Apache 2.0 has been installed from Application Server Companion CD.

The notice further states that the Oracle Enterprise Manager includes the referenced Oracle Fusion Middleware component that is subject to vulnerability but only if one of the above listed affected versions is in use.  Clients with OEM installed are urged to check their Oracle Fusion Middleware versions and patch their installations accordingly.

The Threat is Real

The denial of service vulnerability is in the Apache HTTPD applicable to Oracle HTTP Server products based on Apache versions 2.0 or 2.2.  The nature of the vulnerability is simple yet ominous.  This particular vulnerability may be exploited by a remote user without the need for a username and password.

Further, there is at least one attack tool out that exploits this vulnerability.  The existence of "Apache Killer" has been suspected since at least August.  The potential success of an attack by this or similar means was sufficient to get Oracle moving on a patch.

In addition, Apache Foundation has released Apache HTTP Server 2.2.20 and 2.2.21 to address the flaws in Apache.  It is currently unclear as to whether Oracle has implemented the fixes in Apache HTTP Server 2.2.21 in its own product updates.

How it Works

This vulnerability allows a hacker to mount a denial-of-service attack on the Oracle HTTP server.  It appears that the operating system is not affected; however, a modest number of simultaneous web client requests for overlapping data can quickly overload the server.  This type of attack is fairly simple to launch even without an aggressive tool like "Apache Killer".

Oracle Issues Out-of-Cycle Patch

 The threat posed by this vulernability was sufficently serious to move Oracle to release the patch on an out-of-cycle schedule.  The next scheduled Critical Patch Update is due on October 18, 2011; however, affected and potentially affected Oracle users are urged to deploy the patch as soon as possible.  Out-of-cycle patches from Oracle are not a common occurence, and the sense of urgency inferred from this off-cycle release should filter down to the customer base.