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[USN-8941-1] Squid vulnerabilities

Posted on 20 October 2026
Ubuntu Security

==========================================================================Ubuntu Security Notice USN-8941-1
October 20, 2026

squid, squid3 vulnerabilities
==========================================================================
A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 24.04 LTS
- Ubuntu 22.04 LTS
- Ubuntu 20.04 LTS
- Ubuntu 18.04 LTS
- Ubuntu 16.04 LTS

Summary:

Several security issues were fixed in Squid.

Software Description:
- squid: Web proxy cache server
- squid3: Web proxy cache server

Details:

It was discovered that Squid incorrectly handled certain HTTP Transfer-
Encoding headers. An attacker could possibly use this issue to perform HTTP
request smuggling attacks, bypass security mechanisms, or poison web
caches. (CVE-2026-61642)

It was discovered that Squid incorrectly handled certain cache digest
replies, which could lead to a buffer overflow. A remote attacker could
possibly use this issue to cause Squid to crash, resulting in a denial of
service. This issue only affected Ubuntu 16.04 LTS, Ubuntu 18.04 LTS, and
Ubuntu 20.04 LTS. (CVE-2026-50012)

It was discovered that Squid incorrectly handled parsing certain FTP
directory listings. A remote attacker could possibly use this issue to
obtain sensitive information. This issue only affected Ubuntu 16.04 LTS,
Ubuntu 18.04 LTS, and Ubuntu 20.04 LTS. (CVE-2026-47729)

It was discovered that Squid incorrectly handled certain ICP traffic. A
remote attacker could possibly use this issue to cause Squid to crash,
resulting in a denial of service. This issue only affected Ubuntu 16.04
LTS, Ubuntu 18.04 LTS, and Ubuntu 20.04 LTS. (CVE-2026-32748,
CVE-2026-33526)

It was discovered that Squid incorrectly handled certain ICP requests. A
remote attacker could possibly use this issue to obtain sensitive
information. This issue only affected Ubuntu 16.04 LTS, Ubuntu 18.04 LTS,
and Ubuntu 20.04 LTS. (CVE-2026-33515)

Update instructions:

The problem can be corrected by updating your system to the following
package versions:

Ubuntu 24.04 LTS
squid 6.14-0ubuntu0.24.04.5
squid-openssl 6.14-0ubuntu0.24.04.5

Ubuntu 22.04 LTS
squid 5.9-0ubuntu0.22.04.8
squid-openssl 5.9-0ubuntu0.22.04.8

Ubuntu 20.04 LTS
squid 4.10-1ubuntu1.13+esm3
Available with Ubuntu Pro

Ubuntu 18.04 LTS
squid 3.5.27-1ubuntu1.14+esm6
Available with Ubuntu Pro

Ubuntu 16.04 LTS
squid 3.5.12-1ubuntu7.16+esm7
Available with Ubuntu Pro

In general, a standard system update will make all the necessary changes.

References:
https://ubuntu.com/security/notices/USN-8941-1
CVE-2026-32748, CVE-2026-33515, CVE-2026-33526, CVE-2026-47729,
CVE-2026-50012, CVE-2026-61642

Package Information:
https://launchpad.net/ubuntu/+source/squid/6.14-0ubuntu0.24.04.5
https://launchpad.net/ubuntu/+source/squid/5.9-0ubuntu0.22.04.8

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