CVE-2023-46850 – CVE-2023-46850 is a use-after-free vulnerabilit... (How to Fix)

Q: What is the severity of CVE-2023-46850?

CVE-2023-46850 has a CVSS score of 9.8 (CRITICAL). CVE-2023-46850 is a use-after-free vulnerability in OpenVPN that can lead to memory corruption, information disclosure, or remote code execution when processing network buffers. This affects OpenVPN servers and clients running vulnerable versions. Attackers could potentially exploit this to compromise VPN connections or execute arbitrary code on affected systems.

📋 TL;DR

CVE-2023-46850 is a use-after-free vulnerability in OpenVPN that can lead to memory corruption, information disclosure, or remote code execution when processing network buffers. This affects OpenVPN servers and clients running vulnerable versions. Attackers could potentially exploit this to compromise VPN connections or execute arbitrary code on affected systems.

💻 Affected Systems

Products:

OpenVPN
OpenVPN Access Server

Versions: OpenVPN 2.6.0 through 2.6.6

Operating Systems: Linux, Windows, macOS, BSD systems running affected OpenVPN versions

Default Config Vulnerable: ⚠️ Yes

Notes: Both server and client implementations are affected. OpenVPN Access Server versions before 2.12.0 are vulnerable.

📦 What is this software?

⚠️ Risk & Real-World Impact

🔴

Worst Case

Remote code execution allowing complete system compromise, data exfiltration, and lateral movement through VPN infrastructure.

🟠

Likely Case

Memory corruption leading to service crashes (DoS) or information disclosure of sensitive VPN traffic.

🟢

If Mitigated

Limited to denial of service if exploit attempts are detected and blocked by network controls.

🌐 Internet-Facing: HIGH - OpenVPN servers exposed to the internet are directly vulnerable to remote exploitation.

🏢 Internal Only: MEDIUM - Internal VPN servers could be exploited by authenticated users or through lateral movement.

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: UNKNOWN

Unauthenticated Exploit: ⚠️ Yes

Complexity: MEDIUM

Exploitation requires sending specially crafted network packets to vulnerable OpenVPN instances. No public exploit code has been confirmed as of the advisory dates.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: OpenVPN 2.6.7 or later, OpenVPN Access Server 2.12.0 or later

Vendor Advisory: https://openvpn.net/security-advisory/access-server-security-update-cve-2023-46849-cve-2023-46850/

Restart Required: Yes

Instructions:

1. Update OpenVPN to version 2.6.7 or later using your package manager. 2. For OpenVPN Access Server, update to version 2.12.0 or later. 3. Restart all OpenVPN services after updating. 4. Verify the update was successful by checking the version.

🔧 Temporary Workarounds

Network Segmentation

all

Restrict access to OpenVPN services to trusted networks only

Firewall Rules

linux

Implement strict firewall rules to limit which IPs can connect to OpenVPN ports

iptables -A INPUT -p tcp --dport 1194 -s trusted_ip_range -j ACCEPT
iptables -A INPUT -p udp --dport 1194 -s trusted_ip_range -j ACCEPT

🧯 If You Can't Patch

Implement network-based intrusion detection/prevention systems to monitor for exploit attempts
Consider migrating to alternative VPN solutions if patching is not feasible

🔍 How to Verify

Check if Vulnerable:

Check OpenVPN version: openvpn --version | grep 'OpenVPN'

Check Version:

openvpn --version | head -1

Verify Fix Applied:

Confirm version is 2.6.7 or higher: openvpn --version | grep -E 'OpenVPN (2\.6\.[7-9]|2\.[7-9]|3\.)'

📡 Detection & Monitoring

Log Indicators:

OpenVPN service crashes or restarts
Memory allocation errors in OpenVPN logs
Unusual network buffer processing errors

Network Indicators:

Malformed OpenVPN packets to port 1194 (or custom ports)
Unusual traffic patterns to OpenVPN services

SIEM Query:

source="openvpn.log" AND ("segmentation fault" OR "use after free" OR "memory corruption" OR "buffer overflow")

📊 Metadata

CVE ID: CVE-2023-46850

CVSS v3 Score: 9.8 (CRITICAL)

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

CWE: CWE-416

Published: November 11, 2023

Last Updated: November 21, 2024

🔗 References

📤 Share & Export

📄 Export Markdown 📋 Export JSON

🔗 Related Vulnerabilities

If you're affected by CVE-2023-46850, you might also want to check these: