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[USN-8786-1] rsyslog vulnerability

Posted on 21 September 2026
Ubuntu Security

==========================================================================Ubuntu Security Notice USN-8786-1
September 21, 2026

rsyslog vulnerability
==========================================================================
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

Summary:

rsyslog could be made to crash if it received specially crafted network
traffic.

Software Description:
- rsyslog: Enhanced syslogd

Details:

It was discovered that rsyslog incorrectly calculated buffer sizes when
replacing strings. A remote attacker could possibly use this issue to cause
rsyslog to crash, resulting in a denial of service.

Update instructions:

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

Ubuntu 26.04 LTS
rsyslog 8.2512.0-1ubuntu4.2

Ubuntu 24.04 LTS
rsyslog 8.2312.0-3ubuntu9.4

Ubuntu 22.04 LTS
rsyslog 8.2112.0-2ubuntu2.5

Ubuntu 20.04 LTS
rsyslog 8.2001.0-1ubuntu1.3+esm1
Available with Ubuntu Pro

Ubuntu 18.04 LTS
rsyslog 8.32.0-1ubuntu4.2+esm1
Available with Ubuntu Pro

Ubuntu 16.04 LTS
rsyslog 8.16.0-1ubuntu3.1+esm3
Available with Ubuntu Pro

After a standard system update you need to restart rsyslog to make all the
necessary changes.

References:
https://ubuntu.com/security/notices/USN-8786-1
CVE-2026-78002

Package Information:
https://launchpad.net/ubuntu/+source/rsyslog/8.2512.0-1ubuntu4.2
https://launchpad.net/ubuntu/+source/rsyslog/8.2312.0-3ubuntu9.4
https://launchpad.net/ubuntu/+source/rsyslog/8.2112.0-2ubuntu2.5

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