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USN-5104-1: Squid vulnerability

5 October 2021

Squid could be made to crash or expose sensitive information over the network.



  • squid - Web proxy cache server
  • squid3 - Web proxy cache server


Lyu discovered that Squid incorrectly handled WCCP protocol data. A remote
attacker could use this issue to cause Squid to crash, resulting in a
denial of service, or possibly obtain sensitive information.

Update instructions

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

Ubuntu 21.04
Ubuntu 20.04
Ubuntu 18.04

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