Problem Description:

Due to improper buffer management Squid is vulnerable to a Denial of Service
attack when processing Gopher server responses.

Severity:

This problem allows a remote server to perform Denial of Service when processing
Gopher responses.

CVSS Score of 9.8
https://nvd.nist.gov/vuln-metrics/cvss/v3-calculator?vector=AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H/E:X/RL:X/RC:C/CR:X/IR:X/AR:H/MAV:N/MAC:L/MPR:N/MUI:X/MS:U/MC:X/MI:X/MA:H&version=3.1

Updated Packages:

This bug is fixed by Squid version 5.6.

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

Squid 4:

http://www.squid-cache.org/Versions/v4/SQUID-2021_7.patch

Squid 5:

http://www.squid-cache.org/Versions/v5/SQUID-2021_7.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:

All Squid-3.x up to and including 3.5.28 are vulnerable.

All Squid-4.x up to and including 4.17 are vulnerable.

All Squid-5.x up to and including 5.5 are vulnerable.

Workaround:

Deny access to gopher:// resources by adding the following lines to the top of
squid.conf:

acl gopher proto gopher
http_access deny gopher

Please be mindful that removing port 70 from the Safe_ports ACL definition is not
sufficient. A malicious actor may easily operate gopher servers on other ports.

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 [email protected] 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
http://bugs.squid-cache.org/.

For reporting of security sensitive bugs send an email to the
[email protected] 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 and fixed by Joshua Rogers of Opera Software.

Revision history:

2021-02-20 23:38:06 UTC Initial Report
2022-04-18 13:42:36 UTC Patch Released
2022-04-21 08:29:13 UTC CVE Allocation

END