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[USN-9089-1] x11vnc vulnerability

Posted on 13 November 2026
Ubuntu Security

==========================================================================Ubuntu Security Notice USN-9089-1
November 12, 2026

x11vnc vulnerability
==========================================================================
A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 20.04 LTS

Summary:

x11vnc could be made to expose sensitive information to local users.

Software Description:
- x11vnc: VNC server to allow remote access to an existing X session

Details:

It was discovered that x11vnc created shared memory segments with insecure
permissions. A local attacker could possibly use this issue to obtain
sensitive information or modify screen contents.

Update instructions:

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

Ubuntu 20.04 LTS
x11vnc 0.9.16-3ubuntu0.1~esm2
Available with Ubuntu Pro

After a standard system update you need to restart x11vnc to make all the
necessary changes.

References:
https://ubuntu.com/security/notices/USN-9089-1
CVE-2020-29074

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