CVE-2023-5367

What it actually does

The vulnerability allows an out-of-bounds write in the X server's property change functions due to incorrect buffer offset calculation during heap data copy, resulting in memory corruption that can be leveraged for privilege escalation or denial of service.

Why it matters to the business

Local attackers can gain elevated privileges on affected systems or disrupt graphical sessions, potentially compromising user workstations and requiring urgent updates to prevent exploitation in multi-user environments.

How an attack unfolds

An attacker with local access on a system running the vulnerable X server crafts malicious device or output property change requests that trigger the flawed offset calculation in XIChangeDeviceProperty or RRChangeOutputProperty, writing attacker-controlled data outside allocated buffers to corrupt memory and achieve code execution or crash the server.

How to fix it

Upgrade the xorg-x11-server package to a version containing commit 6197bea02eec072c19aa5365962e89949e674099 or later to correct the buffer offset calculations.

How to confirm the fix worked

Verify the installed X server version includes the fix commit or test by attempting to reproduce the offset miscalculation in a controlled environment; monitor for absence of related memory errors in logs.

Typical attack path

1. Obtain local access to the target system
2. Identify and interact with the X server process
3. Send specially crafted property change requests to trigger the vulnerable functions
4. Exploit the memory corruption for privilege escalation or DoS

How to detect it

Look for unusual crashes or errors in X server logs related to property changes; investigate any unexpected privilege escalations on systems using the X server.

What your security team should do

• Apply the patch to all affected X server installations immediately
• Restrict local access where possible until patched
• Monitor for any post-patch anomalies in graphical sessions