CVE-2024-27903 – CVE-2024-27903 is a critical vulnerability in O... (How to Fix)

Q: What is the severity of CVE-2024-27903?

CVE-2024-27903 has a CVSS score of 9.8 (CRITICAL). CVE-2024-27903 is a critical vulnerability in OpenVPN on Windows where plug-ins can be loaded from any directory, allowing attackers to execute arbitrary code with elevated privileges. This affects OpenVPN 2.6.9 and earlier versions on Windows systems. Attackers can exploit this to gain SYSTEM-level access on vulnerable systems.

📋 TL;DR

CVE-2024-27903 is a critical vulnerability in OpenVPN on Windows where plug-ins can be loaded from any directory, allowing attackers to execute arbitrary code with elevated privileges. This affects OpenVPN 2.6.9 and earlier versions on Windows systems. Attackers can exploit this to gain SYSTEM-level access on vulnerable systems.

💻 Affected Systems

Products:

OpenVPN

Versions: 2.6.9 and earlier

Operating Systems: Windows

Default Config Vulnerable: ⚠️ Yes

Notes: Only affects Windows installations. Linux and other platforms are not vulnerable. Requires plug-in functionality to be enabled, but default configurations are vulnerable.

📦 What is this software?

Openvpn by Openvpn

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Openvpn by Openvpn

View all CVEs affecting Openvpn →

⚠️ Risk & Real-World Impact

🔴

Worst Case

Complete system compromise with SYSTEM privileges, enabling persistent backdoors, credential theft, lateral movement, and full control over the affected system.

🟠

Likely Case

Local privilege escalation leading to administrative access, installation of malware, or data exfiltration from the compromised system.

🟢

If Mitigated

Limited impact with proper access controls, but still presents a significant security risk requiring immediate remediation.

🌐 Internet-Facing: MEDIUM - Requires local access or ability to place malicious plug-in files, but internet-facing OpenVPN servers could be targeted through other initial access vectors.

🏢 Internal Only: HIGH - Internal attackers or compromised accounts can easily exploit this for privilege escalation within the network.

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: LIKELY

Unauthenticated Exploit: ✅ No

Complexity: LOW

Exploitation requires local access to place malicious plug-in files. The vulnerability is straightforward to exploit once initial access is obtained.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: OpenVPN 2.6.10 or later

Vendor Advisory: https://openvpn.net/security-advisory/ovpnx-vulnerability-cve-2024-27903-cve-2024-27459-cve-2024-24974/

Restart Required: Yes

Instructions:

1. Download OpenVPN 2.6.10 or later from the official website. 2. Stop all OpenVPN services. 3. Install the updated version. 4. Restart OpenVPN services. 5. Verify the version is 2.6.10 or higher.

🔧 Temporary Workarounds

Restrict plug-in directory permissions

windows

Set strict permissions on OpenVPN plug-in directories to prevent unauthorized file placement

icacls "C:\Program Files\OpenVPN\plugins" /inheritance:r /grant:r "SYSTEM:(OI)(CI)F" "Administrators:(OI)(CI)F" /deny "Users:(OI)(CI)(W)"
icacls "C:\Program Files\OpenVPN\plugins" /remove:g "Users"

Disable plug-in functionality

all

Remove or disable plug-in loading in OpenVPN configuration

Remove or comment out 'plugin' lines in OpenVPN configuration files

🧯 If You Can't Patch

Implement strict file system permissions on OpenVPN directories to prevent unauthorized file writes
Monitor for suspicious plug-in file creation in OpenVPN directories and restrict user access to these locations

🔍 How to Verify

Check if Vulnerable:

Check OpenVPN version with 'openvpn --version' and verify if it's 2.6.9 or earlier on Windows

Check Version:

openvpn --version

Verify Fix Applied:

Confirm OpenVPN version is 2.6.10 or later using 'openvpn --version'

📡 Detection & Monitoring

Log Indicators:

Unexpected plug-in loading events in OpenVPN logs
File creation events in OpenVPN plug-in directories from non-privileged users

Network Indicators:

Unusual network connections originating from OpenVPN service
Suspicious process execution from OpenVPN context

SIEM Query:

EventID=4688 AND ProcessName LIKE '%openvpn%' AND CommandLine LIKE '%plugin%'

📊 Metadata

CVE ID: CVE-2024-27903

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-283

Published: July 8, 2024

Last Updated: November 21, 2024

🔗 References

https://community.openvpn.net/openvpn/wiki/CVE-2024-27903 Vendor Advisory
https://openvpn.net/security-advisory/ovpnx-vulnerability-cve-2024-27903-cve-2024-27459-cve-2024-24974/ Vendor Advisory
https://www.mail-archive.com/openvpn-users@lists.sourceforge.net/msg07534.html Mailing List
https://community.openvpn.net/openvpn/wiki/CVE-2024-27903 Vendor Advisory
https://openvpn.net/security-advisory/ovpnx-vulnerability-cve-2024-27903-cve-2024-27459-cve-2024-24974/ Vendor Advisory
https://www.mail-archive.com/openvpn-users@lists.sourceforge.net/msg07534.html Mailing List

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