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Ubuntu Security Notice USN-5771-1
December 12, 2022

squid3 regression
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A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 16.04 ESM

Summary:

USN-3557-1 introduced a regression in Squid.

Software Description:
- squid3: Web proxy cache server

Details:

USN-3557-1 fixed vulnerabilities in Squid. This update introduced a
regression which could cause the cache log to be filled with many Vary
loop messages. This update fixes the problem.

We apologize for the inconvenience.

Original advisory details:

Mathias Fischer discovered that Squid incorrectly handled certain long
strings in headers. A malicious remote server could possibly cause Squid to
crash, resulting in a denial of service. This issue was only addressed in
Ubuntu 16.04 LTS. (CVE-2016-2569)

William Lima discovered that Squid incorrectly handled XML parsing when
processing Edge Side Includes (ESI). A malicious remote server could
possibly cause Squid to crash, resulting in a denial of service. This issue
was only addressed in Ubuntu 16.04 LTS. (CVE-2016-2570)

Alex Rousskov discovered that Squid incorrectly handled response-parsing
failures. A malicious remote server could possibly cause Squid to crash,
resulting in a denial of service. This issue only applied to Ubuntu 16.04
LTS. (CVE-2016-2571)

Santiago Ruano Rincón discovered that Squid incorrectly handled certain
Vary headers. A remote attacker could possibly use this issue to cause
Squid to crash, resulting in a denial of service. This issue was only
addressed in Ubuntu 16.04 LTS. (CVE-2016-3948)

Louis Dion-Marcil discovered that Squid incorrectly handled certain Edge
Side Includes (ESI) responses. A malicious remote server could possibly
cause Squid to crash, resulting in a denial of service. (CVE-2018-1000024)

Louis Dion-Marcil discovered that Squid incorrectly handled certain Edge
Side Includes (ESI) responses. A malicious remote server could possibly
cause Squid to crash, resulting in a denial of service. (CVE-2018-1000027)

Update instructions:

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

Ubuntu 16.04 ESM:
  squid                           3.5.12-1ubuntu7.16+esm1

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

References:
  https://ubuntu.com/security/notices/USN-5771-1
  https://launchpad.net/bugs/1999346