--- title: 'USN-4981-1: Squid vulnerabilities | Ubuntu security notices' description: Ubuntu is an open source software operating system that runs from the desktop, to the cloud, to all your internet connected things. url: https://ubuntu.com/security/notices/USN-4981-1 --- 1. [Ubuntu Security Notices](https://ubuntu.com/security/notices) 2. USN-4981-1 --- # USN-4981-1: Squid vulnerabilities Publication date 3 June 2021 Overview Several security issues were fixed in Squid. Releases [21.04](https://ubuntu.com/security/notices?release=hirsute) [20.10](https://ubuntu.com/security/notices?release=groovy) [20.04 LTS](https://ubuntu.com/security/notices?release=focal) [18.04 LTS](https://ubuntu.com/security/notices?release=bionic) --- Open side navigation ## Packages * [squid](https://ubuntu.com/security/cves?package=squid) - Web proxy cache server * [squid3](https://ubuntu.com/security/cves?package=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](https://ubuntu.com/security/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](https://ubuntu.com/security/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. ( --- Show more ## Update instructions In general, a standard system update will make all the necessary changes. [Learn more about how to get the fixes.](https://ubuntu.com/security/cves/about#security) The problem can be corrected by updating your system to the following package versions: | Ubuntu Release | Package Version | | --- | --- | | 21.04 hirsute | [squid](https://launchpad.net/ubuntu/+source/squid) –  [4.13-1ubuntu4.1](https://launchpad.net/ubuntu/+source/squid/4.13-1ubuntu4.1) | | | | 20.10 groovy | [squid](https://launchpad.net/ubuntu/+source/squid) –  [4.13-1ubuntu2.2](https://launchpad.net/ubuntu/+source/squid/4.13-1ubuntu2.2) | | | | 20.04 LTS focal | [squid](https://launchpad.net/ubuntu/+source/squid) –  [4.10-1ubuntu1.4](https://launchpad.net/ubuntu/+source/squid/4.10-1ubuntu1.4) | | | | 18.04 LTS bionic | [squid](https://launchpad.net/ubuntu/+source/squid3) –  [3.5.27-1ubuntu1.11](https://launchpad.net/ubuntu/+source/squid3/3.5.27-1ubuntu1.11) | | | --- ### Reduce your security exposure Ubuntu Pro provides ten-year security coverage to 25,000+ packages in Main and Universe repositories, and it is free for up to five machines. [Get Ubuntu Pro](https://ubuntu.com/pro) ## References * [CVE-2021-33620](https://ubuntu.com/security/CVE-2021-33620) * [CVE-2021-31808](https://ubuntu.com/security/CVE-2021-31808) * [CVE-2021-31807](https://ubuntu.com/security/CVE-2021-31807) * [CVE-2021-31806](https://ubuntu.com/security/CVE-2021-31806) * [CVE-2021-28662](https://ubuntu.com/security/CVE-2021-28662) * [CVE-2021-28652](https://ubuntu.com/security/CVE-2021-28652) * [CVE-2021-28651](https://ubuntu.com/security/CVE-2021-28651) ## Related notices * [USN-6857-1](https://ubuntu.com/security/notices/USN-6857-1)