Due to an Uncontrolled Recursion bug, Squid may be vulnerable to
a Denial of Service attack against HTTP Request parsing.

Severity:

This problem allows a remote client to perform Denial of Service
attack by sending a large X-Forwarded-For header when the
follow_x_forwarded_for feature is configured.

Updated Packages:

This bug is fixed by Squid version 6.6.

In addition, patches addressing this problem for the stable
releases can be found in our patch archives:

Squid 5:

http://www.squid-cache.org/Versions/v5/SQUID-2023_10.patch

Squid 6:

http://www.squid-cache.org/Versions/v6/SQUID-2023_10.patch

If you are using a prepackaged version of Squid then please refer
to the package vendor for availability information on updated
packages.

Determining if your version is vulnerable:

To check for follow_x_forwarded_for run the following command:

squid -k parse 2>&1 |grep follow_x_forwarded_for

All Squid configured without follow_x_forwarded_for are not
vulnerable.

All Squid older than 5.0.5 have not been tested and should be
assumed to be vulnerable when configured with
follow_x_forwarded_for.

All Squid-5.x up to and including 5.9 are vulnerable when
configured with follow_x_forwarded_for.

All Squid-6.x up to and including 6.5 are vulnerable when
configured with follow_x_forwarded_for.

Workaround:

Remove all follow_x_forwarded_for lines from squid.conf

Contact details for the Squid project:

For installation / upgrade support on binary packaged versions
of Squid: Your first point of contact should be your binary
package vendor.

If you install and build Squid from the original Squid sources
then the squid-users@lists.squid-cache.org mailing list is your
primary support point. For subscription details see
http://www.squid-cache.org/Support/mailing-lists.html.

For reporting of non-security bugs in the latest STABLE release
the squid bugzilla database should be used
https://bugs.squid-cache.org/.

For reporting of security sensitive bugs send an email to the
squid-bugs@lists.squid-cache.org mailing list. It's a closed
list (though anyone can post) and security related bug reports
are treated in confidence until the impact has been established.

Credits:

This vulnerability was discovered by Joshua Rogers of Opera
Software.

Fixed by Thomas Leroy of the SUSE security team.

Revision history:

2023-10-12 11:53:02 UTC Initial Report
2023-11-28 07:35:46 UTC Patches Released

END