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If through a vulnerability assessment, a network security issue is detected for the vulnerability below, applying the appropriate security patches in a timely matter is very important. If you have detected that your system has already been compromised, following CERT's Network Security recovery document will assist with recommended steps for system recovery.
Vulnerability Assessment Details
Squid ACL [url_regex] bypass vulnerability
Detailed Explanation for this Vulnerability Assessment
The remote host is affected by the vulnerability described in GLSA-200403-11
(Squid ACL [url_regex] bypass vulnerability)
A bug in Squid permits users to bypass certain access controls by passing a
URL containing "%00" which exploits the Squid decoding function.
This may insert a NUL character into decoded URLs, which may permit users to
bypass url_regex access control lists that are enforced upon them.
In such a scenario, Squid will insert a NUL character after
the"%00" and it will make a comparison between the URL to the end
of the NUL character rather than the contents after it: the comparison does
not result in a match, and the user's request is not denied.
Restricted users may be able to bypass url_regex access control lists that
are enforced upon them which may cause unwanted network traffic as well as
a route for other possible exploits. Users of Squid 2.5STABLE4 and below
who require the url_regex features are recommended to upgrade to 2.5STABLE5
to maintain the security of their infrastructure.
A workaround is not currently known for this issue. All users are advised
to upgrade to the latest version of Squid.
Squid can be updated as follows:
# emerge sync
# emerge -pv ">=www-proxy/squid-2.5.5"
# emerge ">=www-proxy/squid-2.5.5"
Network Security Threat Level: Medium
Networks Security ID:
Vulnerability Assessment Copyright: (C) 2005 Michel Arboi
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