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Ubuntu Security Notice USN-4446-1
August 03, 2020

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

- Ubuntu 18.04 LTS
- Ubuntu 16.04 LTS

Summary:

Several security issues were fixed in Squid.

Software Description:
- squid3: Web proxy cache server

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                           3.5.27-1ubuntu1.7

Ubuntu 16.04 LTS:
  squid                           3.5.12-1ubuntu7.12

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

References:
  https://usn.ubuntu.com/4446-1
  CVE-2019-12520, CVE-2019-12523, CVE-2019-12524, CVE-2019-18676

Package Information:
  https://launchpad.net/ubuntu/+source/squid3/3.5.27-1ubuntu1.7
  https://launchpad.net/ubuntu/+source/squid3/3.5.12-1ubuntu7.12