CVE-2023-6377 – This vulnerability in xorg-server allows out-of... (How to Fix)

Q: What is the severity of CVE-2023-6377?

CVE-2023-6377 has a CVSS score of 7.8 (HIGH). This vulnerability in xorg-server allows out-of-bounds memory reads and writes when querying or changing XKB button actions, such as switching from touchpad to mouse. It could enable local privilege escalation or remote code execution when X11 forwarding is used. Systems running affected versions of xorg-server with X11 enabled are at risk.

📋 TL;DR

This vulnerability in xorg-server allows out-of-bounds memory reads and writes when querying or changing XKB button actions, such as switching from touchpad to mouse. It could enable local privilege escalation or remote code execution when X11 forwarding is used. Systems running affected versions of xorg-server with X11 enabled are at risk.

💻 Affected Systems

Products:

xorg-server

Versions: Versions before the patched releases (specific versions vary by distribution)

Operating Systems: Linux distributions using xorg-server, Unix-like systems with X11

Default Config Vulnerable: ⚠️ Yes

Notes: Systems with X11 enabled and XKB functionality are vulnerable. X11 forwarding increases attack surface.

📦 What is this software?

⚠️ Risk & Real-World Impact

🔴

Worst Case

Remote code execution via X11 forwarding leading to full system compromise

🟠

Likely Case

Local privilege escalation allowing attackers to gain root access

🟢

If Mitigated

Denial of service or limited information disclosure if memory protections are in place

🌐 Internet-Facing: MEDIUM - Requires X11 forwarding to be exposed, which is less common

🏢 Internal Only: HIGH - Local exploitation is straightforward and X11 is commonly used internally

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: UNKNOWN

Unauthenticated Exploit: ✅ No

Complexity: MEDIUM

Requires local access or X11 forwarding. Memory corruption exploitation requires specific conditions.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: Varies by distribution - check Red Hat advisories for specific versions

Vendor Advisory: https://access.redhat.com/errata/RHSA-2023:7886

Restart Required: Yes

Instructions:

1. Update xorg-server package using your distribution's package manager. 2. For Red Hat systems: 'yum update xorg-server'. 3. Restart X11 session or reboot system.

🔧 Temporary Workarounds

Disable X11 Forwarding

linux

Prevent remote exploitation by disabling X11 forwarding in SSH configuration

Set 'X11Forwarding no' in /etc/ssh/sshd_config
Restart SSH: 'systemctl restart sshd'

Restrict X11 Access

linux

Limit X11 server access to trusted users only

Use 'xhost' to manage access: 'xhost -' to disable all access
'xhost +si:localuser:username' to allow specific users

🧯 If You Can't Patch

Disable X11 forwarding completely in SSH and application configurations
Implement strict access controls and monitor for unusual X11 activity

🔍 How to Verify

Check if Vulnerable:

Check xorg-server version: 'rpm -q xorg-server' (Red Hat) or 'apt list --installed | grep xorg-server' (Debian)

Check Version:

xorg-server --version or package manager query

Verify Fix Applied:

Verify updated version matches patched release from vendor advisory

📡 Detection & Monitoring

Log Indicators:

X11 crash logs
Memory access violation errors in system logs
Unusual XKB-related activity

Network Indicators:

X11 forwarding connections from unexpected sources
Unusual X protocol traffic

SIEM Query:

source="xorg.log" AND ("segmentation fault" OR "out of bounds" OR "XKB")

📊 Metadata

CVE ID: CVE-2023-6377

CVSS v3 Score: 7.8 (HIGH)

CVSS Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

CWE: CWE-787

Published: December 13, 2023

Last Updated: February 25, 2026

🔗 References

📤 Share & Export

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🔗 Related Vulnerabilities

If you're affected by CVE-2023-6377, you might also want to check these:

📋 TL;DR

💻 Affected Systems

📦 What is this software?

Debian Linux by Debian

Debian Linux by Debian

Debian Linux by Debian

Enterprise Linux Eus by Redhat

Tigervnc by Tigervnc

X Server by X.org

Xwayland by X.org

⚠️ Risk & Real-World Impact

Worst Case

Likely Case

If Mitigated

🎯 Exploit Status

🛠️ Fix & Mitigation

✅ Official Fix

Instructions:

🔧 Temporary Workarounds

Disable X11 Forwarding

Restrict X11 Access

🧯 If You Can't Patch

🔍 How to Verify

Check if Vulnerable:

Check Version:

Verify Fix Applied:

📡 Detection & Monitoring

Log Indicators:

Network Indicators:

SIEM Query:

📊 Metadata

🔗 References

📤 Share & Export

🔗 Related Vulnerabilities