A Squid security update has been released for Ubuntu Linux 18.04 LTS, 20.04 LTS, 20.10, and 21.04.

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Ubuntu Security Notice USN-4981-1
June 03, 2021

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

- Ubuntu 21.04
- Ubuntu 20.10
- Ubuntu 20.04 LTS
- Ubuntu 18.04 LTS

Summary:

Several security issues were fixed in Squid.

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

Details:

Joshua Rogers discovered that Squid incorrectly handled requests with the
urn: scheme. A remote attacker could possibly use this issue to cause
Squid to consume resources, leading to a denial of service.
(CVE-2021-28651)

Joshua Rogers discovered that Squid incorrectly handled requests to the
Cache Manager API. A remote attacker with access privileges could possibly
use this issue to cause Squid to consume resources, leading to a denial of
service. This issue was only addressed in Ubuntu 20.04 LTS, Ubuntu 20.10,
and Ubuntu 21.04. (CVE-2021-28652)

Joshua Rogers discovered that Squid incorrectly handled certain response
headers. A remote attacker could possibly use this issue to cause Squid to
crash, resulting in a denial of service. This issue was only affected
Ubuntu 20.04 LTS, Ubuntu 20.10, and Ubuntu 21.04. (CVE-2021-28662)

Joshua Rogers discovered that Squid incorrectly handled range request
processing. A remote attacker could possibly use this issue to cause Squid
to crash, resulting in a denial of service. (CVE-2021-31806,
CVE-2021-31807, CVE-2021-31808)

Joshua Rogers discovered that Squid incorrectly handled certain HTTP
responses. A remote attacker could possibly use this issue to cause Squid
to crash, resulting in a denial of service. (CVE-2021-33620)

Update instructions:

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

Ubuntu 21.04:
squid 4.13-1ubuntu4.1

Ubuntu 20.10:
squid 4.13-1ubuntu2.2

Ubuntu 20.04 LTS:
squid 4.10-1ubuntu1.4

Ubuntu 18.04 LTS:
squid 3.5.27-1ubuntu1.11

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

References:
  https://ubuntu.com/security/notices/USN-4981-1
CVE-2021-28651, CVE-2021-28652, CVE-2021-28662, CVE-2021-31806,
CVE-2021-31807, CVE-2021-31808, CVE-2021-33620

Package Information:
  https://launchpad.net/ubuntu/+source/squid/4.13-1ubuntu4.1
  https://launchpad.net/ubuntu/+source/squid/4.13-1ubuntu2.2
  https://launchpad.net/ubuntu/+source/squid/4.10-1ubuntu1.4
  https://launchpad.net/ubuntu/+source/squid3/3.5.27-1ubuntu1.11