[USN-8144-1] Undertow vulnerability

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Ubuntu Security Notice USN-8144-1
April 02, 2026

undertow vulnerability
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A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 24.04 LTS
- Ubuntu 22.04 LTS
- Ubuntu 20.04 LTS
- Ubuntu 18.04 LTS
- Ubuntu 16.04 LTS

Summary:

Undertow would allow unintended access to user sessions over the network.

Software Description:
- undertow: Java web server based on non-blocking IO

Details:

It was discovered that Undertow incorrectly validated the Host header in
incoming HTTP requests. A remote attacker could possibly use this issue
to gain unintended access to user sessions.

Update instructions:

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

Ubuntu 24.04 LTS
libundertow-java 2.3.8-2ubuntu0.1~esm1
Available with Ubuntu Pro

Ubuntu 22.04 LTS
libundertow-java 2.2.16-1ubuntu0.1~esm1
Available with Ubuntu Pro

Ubuntu 20.04 LTS
libundertow-java 2.0.29-1ubuntu0.1~esm1
Available with Ubuntu Pro

Ubuntu 18.04 LTS
libundertow-java 1.4.23-3ubuntu0.1~esm1
Available with Ubuntu Pro

Ubuntu 16.04 LTS
libundertow-java 1.3.16-1ubuntu0.1~esm1
Available with Ubuntu Pro

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

References:
https://ubuntu.com/security/notices/USN-8144-1
CVE-2025-12543