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Ubuntu Security Notice USN-4446-2
August 27, 2020

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

- Ubuntu 18.04 LTS
- Ubuntu 16.04 LTS

Summary:

USN-4446-1 introduced a regression in Squid.

Software Description:
- squid3: Web proxy cache server

Details:

USN-4446-1 fixed vulnerabilities in Squid. The update introduced a
regression when using Squid with the icap or ecap protocols. This update
fixes the problem.

We apologize for the inconvenience.

Original advisory details:

 Jeriko One discovered that Squid incorrectly handled caching certain
 requests. A remote attacker could possibly use this issue to perform
 cache-injection attacks or gain access to reverse proxy features such as
 ESI. (CVE-2019-12520)
  Jeriko One and Kristoffer Danielsson discovered that Squid incorrectly
 handled certain URN requests. A remote attacker could possibly use this
 issue to bypass access checks. (CVE-2019-12523)
  Jeriko One discovered that Squid incorrectly handled URL decoding. A remote
 attacker could possibly use this issue to bypass certain rule checks.
 (CVE-2019-12524)
  Jeriko One and Kristoffer Danielsson discovered that Squid incorrectly
 handled input validation. A remote attacker could use this issue to cause
 Squid to crash, resulting in a denial of service. (CVE-2019-18676)

Update instructions:

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

Ubuntu 18.04 LTS:
  squid                           3.5.27-1ubuntu1.8

Ubuntu 16.04 LTS:
  squid                           3.5.12-1ubuntu7.13

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

References:
  https://usn.ubuntu.com/4446-2
  https://usn.ubuntu.com/4446-1
  https://launchpad.net/bugs/1890265

Package Information:
  https://launchpad.net/ubuntu/+source/squid3/3.5.27-1ubuntu1.8
  https://launchpad.net/ubuntu/+source/squid3/3.5.12-1ubuntu7.13