Due to a buffer overflow bug Squid is vulnerable to a Denial of
Service attack against HTTP Digest Authentication

Severity:

This problem allows a remote client to perform buffer overflow
attack writing up to 2 MB of arbitrary data to heap memory
when Squid is configured to accept HTTP Digest Authentication.

On machines with advanced memory protections this will result
in a Denial of Service against all users of the Squid proxy.

CVSS Score of 9.9
https://nvd.nist.gov/vuln-metrics/cvss/v3-calculator?vector=AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:H&version=3.1

Updated Packages:

This bug is fixed by Squid version 6.4.

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_3.patch

Squid 6:

http://www.squid-cache.org/Versions/v6/SQUID-2023_3.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:

Squid older than 5.0.5 have not been tested and should be assumed
to be vulnerable.

All Squid-5.0.6 up to and including 5.9 are vulnerable.

All Squid-6.x up to and including 6.3 are vulnerable.

Workaround:

Disable HTTP Digest authentication until Squid can be
upgraded or patched.

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 Alex Bason.

Revision history:

2021-03-22 00:59:20 UTC Initial Report
2023-10-13 17:31:11 UTC Patch Published

END