USN-8840-1: libevent vulnerabilities

Publication date

28 September 2026

Overview

Several security issues were fixed in libevent.


Packages

Details

Michał Majchrowicz and Marcin Wyczechowski discovered that libevent
incorrectly handled certain DNS responses. A remote attacker could possibly
use this issue to cause a denial of service or execute arbitrary code.
(CVE-2026-63387)

It was discovered that libevent incorrectly handled certain connections. A
local attacker could possibly use this issue to cause a denial of service
or execute arbitrary code. This issue only affected Ubuntu 18.04 LTS,
Ubuntu 20.04 LTS, Ubuntu 22.04 LTS, Ubuntu 24.04 LTS, and Ubuntu 26.04 LTS.
(CVE-2026-63388)

Michał Majchrowicz and Marcin Wyczechowski discovered that libevent
incorrectly handled certain DNS responses. A remote attacker could possibly
use this issue to cause a denial of service or execute arbitrary code.
(CVE-2026-63387)

It was discovered that libevent incorrectly handled certain connections. A
local attacker could possibly use this issue to cause a denial of service
or execute arbitrary code. This issue only affected Ubuntu 18.04 LTS,
Ubuntu 20.04 LTS, Ubuntu 22.04 LTS, Ubuntu 24.04 LTS, and Ubuntu 26.04 LTS.
(CVE-2026-63388)

Update instructions

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

Learn more about how to get the fixes.

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

Ubuntu Release Package Version
26.04 LTS resolute libevent-2.1-7t64 –  2.1.12-stable-10ubuntu0.2
libevent-core-2.1-7t64 –  2.1.12-stable-10ubuntu0.2
libevent-dev –  2.1.12-stable-10ubuntu0.2
libevent-extra-2.1-7t64 –  2.1.12-stable-10ubuntu0.2
libevent-openssl-2.1-7t64 –  2.1.12-stable-10ubuntu0.2
libevent-pthreads-2.1-7t64 –  2.1.12-stable-10ubuntu0.2
24.04 LTS noble libevent-2.1-7t64 –  2.1.12-stable-9ubuntu2.2
libevent-core-2.1-7t64 –  2.1.12-stable-9ubuntu2.2
libevent-dev –  2.1.12-stable-9ubuntu2.2
libevent-extra-2.1-7t64 –  2.1.12-stable-9ubuntu2.2
libevent-openssl-2.1-7t64 –  2.1.12-stable-9ubuntu2.2
libevent-pthreads-2.1-7t64 –  2.1.12-stable-9ubuntu2.2
22.04 LTS jammy libevent-2.1-7 –  2.1.12-stable-1ubuntu0.2
libevent-core-2.1-7 –  2.1.12-stable-1ubuntu0.2
libevent-dev –  2.1.12-stable-1ubuntu0.2
libevent-extra-2.1-7 –  2.1.12-stable-1ubuntu0.2
libevent-openssl-2.1-7 –  2.1.12-stable-1ubuntu0.2
libevent-pthreads-2.1-7 –  2.1.12-stable-1ubuntu0.2
20.04 LTS focal libevent-2.1-7 –  2.1.11-stable-1ubuntu0.1~esm2  
libevent-core-2.1-7 –  2.1.11-stable-1ubuntu0.1~esm2  
libevent-dev –  2.1.11-stable-1ubuntu0.1~esm2  
libevent-extra-2.1-7 –  2.1.11-stable-1ubuntu0.1~esm2  
libevent-openssl-2.1-7 –  2.1.11-stable-1ubuntu0.1~esm2  
libevent-pthreads-2.1-7 –  2.1.11-stable-1ubuntu0.1~esm2  
18.04 LTS bionic libevent-2.1-6 –  2.1.8-stable-4ubuntu0.1~esm2  
libevent-core-2.1-6 –  2.1.8-stable-4ubuntu0.1~esm2  
libevent-dev –  2.1.8-stable-4ubuntu0.1~esm2  
libevent-extra-2.1-6 –  2.1.8-stable-4ubuntu0.1~esm2  
libevent-openssl-2.1-6 –  2.1.8-stable-4ubuntu0.1~esm2  
libevent-pthreads-2.1-6 –  2.1.8-stable-4ubuntu0.1~esm2  
16.04 LTS xenial libevent-2.0-5 –  2.0.21-stable-2ubuntu0.16.04.1+esm2  
libevent-core-2.0-5 –  2.0.21-stable-2ubuntu0.16.04.1+esm2  
libevent-dev –  2.0.21-stable-2ubuntu0.16.04.1+esm2  
libevent-extra-2.0-5 –  2.0.21-stable-2ubuntu0.16.04.1+esm2  
libevent-openssl-2.0-5 –  2.0.21-stable-2ubuntu0.16.04.1+esm2  
libevent-pthreads-2.0-5 –  2.0.21-stable-2ubuntu0.16.04.1+esm2  
14.04 LTS trusty libevent-2.0-5 –  2.0.21-stable-1ubuntu1.14.04.2+esm2  
libevent-core-2.0-5 –  2.0.21-stable-1ubuntu1.14.04.2+esm2  
libevent-dev –  2.0.21-stable-1ubuntu1.14.04.2+esm2  
libevent-extra-2.0-5 –  2.0.21-stable-1ubuntu1.14.04.2+esm2  
libevent-openssl-2.0-5 –  2.0.21-stable-1ubuntu1.14.04.2+esm2  
libevent-pthreads-2.0-5 –  2.0.21-stable-1ubuntu1.14.04.2+esm2  

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