--- title: 'USN-4891-1: OpenSSL vulnerability | 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-4891-1 --- 1. [Ubuntu Security Notices](https://ubuntu.com/security/notices) 2. USN-4891-1 --- # USN-4891-1: OpenSSL vulnerability Publication date 25 March 2021 Overview OpenSSL could be made to crash if it received specially crafted network traffic. Releases [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 * [openssl](https://ubuntu.com/security/cves?package=openssl) - Secure Socket Layer (SSL) cryptographic library and tools ## Details It was discovered that OpenSSL incorrectly handled certain renegotiation ClientHello messages. A remote attacker could use this issue to cause OpenSSL to crash, resulting in a denial of service. ## Update instructions After a standard system update you need to reboot your computer to 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 | | --- | --- | | 20.10 groovy | [libssl1.1](https://launchpad.net/ubuntu/+source/openssl) –  [1.1.1f-1ubuntu4.3](https://launchpad.net/ubuntu/+source/openssl/1.1.1f-1ubuntu4.3) | | | | 20.04 LTS focal | [libssl1.1](https://launchpad.net/ubuntu/+source/openssl) –  [1.1.1f-1ubuntu2.3](https://launchpad.net/ubuntu/+source/openssl/1.1.1f-1ubuntu2.3) | | | | 18.04 LTS bionic | [libssl1.1](https://launchpad.net/ubuntu/+source/openssl) –  [1.1.1-1ubuntu2.1~18.04.9](https://launchpad.net/ubuntu/+source/openssl/1.1.1-1ubuntu2.1~18.04.9) | | | --- ### 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-2021-3449](https://ubuntu.com/security/CVE-2021-3449) ## Related notices * [USN-5038-1](https://ubuntu.com/security/notices/USN-5038-1)