# x11vnc vulnerability in Ubuntu 20.04 LTS allows local information exposure

> **Key takeaway:** A flaw in x11vnc's shared memory segment permissions allows local attackers to access sensitive screen data or modify visual content.

**Published:** 2026-11-12T20:55:34+00:00 
**Source:** Ubuntu Security & Release Notices 
**Category:** distro-news 
**Canonical URL:** https://fosswire.org/news/x11vnc-vulnerability-in-ubuntu-2004-lts-allows-local-informa.html 

## Summary
Ubuntu has issued a security notice regarding a vulnerability in the x11vnc package, which provides remote access to existing X11 sessions. The flaw involves the creation of shared memory segments with insecure permissions, potentially exposing the desktop session to unauthorized users.

A local attacker can exploit this weakness to either intercept sensitive information displayed on the screen or manipulate the visual contents of the session. The fix is currently available for Ubuntu 20.04 LTS users through the Ubuntu Pro ESM (Expanded Security Maintenance) repository.

## Technical details of CVE-2020-29074
- **Defect Class:** Insecure shared memory segment permissions.
- **Attack Vector:** Local access is required to exploit the vulnerability.
- **Impact:** Potential for sensitive information disclosure or unauthorized modification of screen contents.
- **Mitigation:** Users must update to x11vnc version 0.9.16-3ubuntu0.1~esm2 and restart the x11vnc service to apply the fix.

## Why it matters
This vulnerability highlights the risks associated with legacy X11 remote access tools in multi-user environments. Because the fix is delivered via Ubuntu Pro ESM, users on the 20.04 LTS cycle must have an active Ubuntu Pro subscription to receive the security patch for this Universe repository package.