Title: ActivePerl perlIIS.dll Buffer Overflow Vulnerability
Severity: CRITICAL
Description:
ActivePerl is an implementation of the Perl scripting language for Microsoft Windows systems developed by Activestate. ActivePerl allows for high-performance integration with IIS using a DLL called 'perlIIS.dll' to handle a '.plx' ISAPI extension.
perlIIS.dll contains a remotely exploitable buffer overflow vulnerability in handling of the URL string. When an attacker supplies an excessively long filename with a '.plx' extension, an unbounded string copy results in a stack overflow.
Since the request is client-supplied, an attacker can replace the return address of the affected function with an arbitrary value when the overflow occurs. Arbitrary code can be executed by placing instructions on the stack and overwriting the return address with a pointer to them. When the function returns, the instructions will be executed.
All versions of ActivePerl prior to build 630 of ActivePerl 5.6.1 are believed to be vulnerable. While the file extension '.plx' is associated with perlIIS.dll by default, administrators may have mapped '.pl' to the same service, making this file extension exploitable as well.
Exploitation of this vulnerability may allow for remote attackers to gain access to the target server. Code will be executed in the security context of IWAM_hostname in IIS 5.0 and Local SYSTEM in IIS 4.0. This vulnerability requires that the option "Check that file exists" be disabled. This option is enabled by default.
Affected Products:
- Activestate ActivePerl 5.6.1
References:
- Activestate: ActivePerl Homepage
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