--- title: 'USN-5201-1: Python 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-5201-1 --- 1. [Ubuntu Security Notices](https://ubuntu.com/security/notices) 2. USN-5201-1 --- # USN-5201-1: Python vulnerabilities Publication date 17 December 2021 Overview Python could be made to crash if it receives specially crafted input from a malicious server. Releases [21.04](https://ubuntu.com/security/notices?release=hirsute) [20.04 LTS](https://ubuntu.com/security/notices?release=focal) --- Open side navigation ## Packages * [python3.8](https://ubuntu.com/security/cves?package=python3.8) - An interactive high-level object-oriented language * [python3.9](https://ubuntu.com/security/cves?package=python3.9) - Interactive high-level object-oriented language (version 3.9) ## Details It was discovered that the Python urllib http client could enter into an infinite loop when incorrectly handling certain server responses (100 Continue response). Specially crafted traffic from a malicious HTTP server could cause a denial of service (Dos) condition for a client. ## 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 | [python3.9-minimal](https://launchpad.net/ubuntu/+source/python3.9) –  [3.9.5-3ubuntu0~21.04.1](https://launchpad.net/ubuntu/+source/python3.9/3.9.5-3ubuntu0~21.04.1) | | | | [libpython3.9-stdlib](https://launchpad.net/ubuntu/+source/python3.9) –  [3.9.5-3ubuntu0~21.04.1](https://launchpad.net/ubuntu/+source/python3.9/3.9.5-3ubuntu0~21.04.1) | | | | [python3.9](https://launchpad.net/ubuntu/+source/python3.9) –  [3.9.5-3ubuntu0~21.04.1](https://launchpad.net/ubuntu/+source/python3.9/3.9.5-3ubuntu0~21.04.1) | | | | 20.04 LTS focal | [python3.9-minimal](https://launchpad.net/ubuntu/+source/python3.9) –  [3.9.5-3ubuntu0~20.04.1](https://launchpad.net/ubuntu/+source/python3.9/3.9.5-3ubuntu0~20.04.1) | | | | [python3.9](https://launchpad.net/ubuntu/+source/python3.9) –  [3.9.5-3ubuntu0~20.04.1](https://launchpad.net/ubuntu/+source/python3.9/3.9.5-3ubuntu0~20.04.1) | | | | [libpython3.8-stdlib](https://launchpad.net/ubuntu/+source/python3.8) –  [3.8.10-0ubuntu1~20.04.2](https://launchpad.net/ubuntu/+source/python3.8/3.8.10-0ubuntu1~20.04.2) | | | | [python3.8](https://launchpad.net/ubuntu/+source/python3.8) –  [3.8.10-0ubuntu1~20.04.2](https://launchpad.net/ubuntu/+source/python3.8/3.8.10-0ubuntu1~20.04.2) | | | | [python3.8-minimal](https://launchpad.net/ubuntu/+source/python3.8) –  [3.8.10-0ubuntu1~20.04.2](https://launchpad.net/ubuntu/+source/python3.8/3.8.10-0ubuntu1~20.04.2) | | | | [libpython3.9-stdlib](https://launchpad.net/ubuntu/+source/python3.9) –  [3.9.5-3ubuntu0~20.04.1](https://launchpad.net/ubuntu/+source/python3.9/3.9.5-3ubuntu0~20.04.1) | | | --- ### 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-2021-3737](https://ubuntu.com/security/CVE-2021-3737) ## Related notices * [USN-6891-1](https://ubuntu.com/security/notices/USN-6891-1) * [USN-5200-1](https://ubuntu.com/security/notices/USN-5200-1) * [USN-5199-1](https://ubuntu.com/security/notices/USN-5199-1) * [USN-5083-1](https://ubuntu.com/security/notices/USN-5083-1)