Home / mailings [USN-8840-1] libevent vulnerabilities
Posted on 29 September 2026
Ubuntu Security==========================================================================Ubuntu Security Notice USN-8840-1
September 28, 2026
libevent vulnerabilities
==========================================================================
A security issue affects these releases of Ubuntu and its derivatives:
- Ubuntu 26.04 LTS
- Ubuntu 24.04 LTS
- Ubuntu 22.04 LTS
- Ubuntu 20.04 LTS
- Ubuntu 18.04 LTS
- Ubuntu 16.04 LTS
- Ubuntu 14.04 LTS
Summary:
Several security issues were fixed in libevent.
Software Description:
- libevent: Event notification library
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)
Update instructions:
The problem can be corrected by updating your system to the following
package versions:
Ubuntu 26.04 LTS
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
Ubuntu 24.04 LTS
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
Ubuntu 22.04 LTS
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
Ubuntu 20.04 LTS
libevent-2.1-7 2.1.11-stable-1ubuntu0.1~esm2
Available with Ubuntu Pro
libevent-core-2.1-7 2.1.11-stable-1ubuntu0.1~esm2
Available with Ubuntu Pro
libevent-dev 2.1.11-stable-1ubuntu0.1~esm2
Available with Ubuntu Pro
libevent-extra-2.1-7 2.1.11-stable-1ubuntu0.1~esm2
Available with Ubuntu Pro
libevent-openssl-2.1-7 2.1.11-stable-1ubuntu0.1~esm2
Available with Ubuntu Pro
libevent-pthreads-2.1-7 2.1.11-stable-1ubuntu0.1~esm2
Available with Ubuntu Pro
Ubuntu 18.04 LTS
libevent-2.1-6 2.1.8-stable-4ubuntu0.1~esm2
Available with Ubuntu Pro
libevent-core-2.1-6 2.1.8-stable-4ubuntu0.1~esm2
Available with Ubuntu Pro
libevent-dev 2.1.8-stable-4ubuntu0.1~esm2
Available with Ubuntu Pro
libevent-extra-2.1-6 2.1.8-stable-4ubuntu0.1~esm2
Available with Ubuntu Pro
libevent-openssl-2.1-6 2.1.8-stable-4ubuntu0.1~esm2
Available with Ubuntu Pro
libevent-pthreads-2.1-6 2.1.8-stable-4ubuntu0.1~esm2
Available with Ubuntu Pro
Ubuntu 16.04 LTS
libevent-2.0-5 2.0.21-stable-2ubuntu0.16.04.1+esm2
Available with Ubuntu Pro
libevent-core-2.0-5 2.0.21-stable-2ubuntu0.16.04.1+esm2
Available with Ubuntu Pro
libevent-dev 2.0.21-stable-2ubuntu0.16.04.1+esm2
Available with Ubuntu Pro
libevent-extra-2.0-5 2.0.21-stable-2ubuntu0.16.04.1+esm2
Available with Ubuntu Pro
libevent-openssl-2.0-5 2.0.21-stable-2ubuntu0.16.04.1+esm2
Available with Ubuntu Pro
libevent-pthreads-2.0-5 2.0.21-stable-2ubuntu0.16.04.1+esm2
Available with Ubuntu Pro
Ubuntu 14.04 LTS
libevent-2.0-5 2.0.21-stable-1ubuntu1.14.04.2+esm2
Available with Ubuntu Pro
libevent-core-2.0-5 2.0.21-stable-1ubuntu1.14.04.2+esm2
Available with Ubuntu Pro
libevent-dev 2.0.21-stable-1ubuntu1.14.04.2+esm2
Available with Ubuntu Pro
libevent-extra-2.0-5 2.0.21-stable-1ubuntu1.14.04.2+esm2
Available with Ubuntu Pro
libevent-openssl-2.0-5 2.0.21-stable-1ubuntu1.14.04.2+esm2
Available with Ubuntu Pro
libevent-pthreads-2.0-5 2.0.21-stable-1ubuntu1.14.04.2+esm2
Available with Ubuntu Pro
In general, a standard system update will make all the necessary changes.
References:
https://ubuntu.com/security/notices/USN-8840-1
CVE-2026-63387, CVE-2026-63388
Package Information:
https://launchpad.net/ubuntu/+source/libevent/2.1.12-stable-10ubuntu0.2
https://launchpad.net/ubuntu/+source/libevent/2.1.12-stable-9ubuntu2.2
https://launchpad.net/ubuntu/+source/libevent/2.1.12-stable-1ubuntu0.2
--===============0377755512122826290==Content-Type: application/pgp-signature; name="signature.asc"
Content-Description: OpenPGP digital signature
