CVE-2022-0547
📋 TL;DR
This vulnerability allows authentication bypass in OpenVPN when using external authentication plugins with deferred authentication replies. Attackers can gain access with only partially correct credentials. Affects OpenVPN servers using external authentication plugins with deferred authentication.
💻 Affected Systems
- OpenVPN
📦 What is this software?
Fedora by Fedoraproject
Fedora by Fedoraproject
Openvpn by Openvpn
Openvpn by Openvpn
⚠️ Risk & Real-World Impact
Worst Case
Unauthorized users gain full VPN access to internal networks, potentially leading to data exfiltration, lateral movement, and complete network compromise.
Likely Case
Attackers bypass authentication to access VPN-protected resources, potentially accessing sensitive systems and data.
If Mitigated
With proper network segmentation and monitoring, impact limited to initial VPN access with detection of anomalous authentication attempts.
🎯 Exploit Status
Requires knowledge of external authentication plugin configuration and ability to craft authentication attempts.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: OpenVPN 2.4.13, 2.5.7, or later
Vendor Advisory: https://community.openvpn.net/openvpn/wiki/CVE-2022-0547
Restart Required: Yes
Instructions:
1. Download latest OpenVPN version from official sources. 2. Stop OpenVPN service. 3. Install updated version. 4. Restart OpenVPN service. 5. Verify version with 'openvpn --version'.
🔧 Temporary Workarounds
Disable deferred authentication
allConfigure external authentication plugins to not use deferred authentication replies
Modify OpenVPN server configuration to set 'plugin' options appropriately
Use internal authentication
allSwitch from external authentication plugins to built-in authentication methods
Modify OpenVPN server configuration to use 'auth-user-pass-verify' or similar built-in methods
🧯 If You Can't Patch
- Implement network segmentation to limit VPN access to critical systems
- Enable detailed authentication logging and monitor for anomalous access patterns
🔍 How to Verify
Check if Vulnerable:
Check OpenVPN version with 'openvpn --version' and verify if using external authentication plugins with deferred authentication.Check Version:
openvpn --versionVerify Fix Applied:
Confirm OpenVPN version is 2.4.13+, 2.5.7+, or later with 'openvpn --version'.📡 Detection & Monitoring
Log Indicators:
- Multiple authentication attempts from same user with varying credentials
- Successful authentication after previously failed attempts
- Authentication plugin errors or warnings
Network Indicators:
- Unusual VPN connection patterns
- Access from unexpected locations or IPs
SIEM Query:
source="openvpn.log" AND ("authentication" OR "auth") AND ("failed" NEAR "success")🔗 References
- https://community.openvpn.net/openvpn/wiki/CVE-2022-0547
- https://community.openvpn.net/openvpn/wiki/SecurityAnnouncements
- https://lists.debian.org/debian-lts-announce/2022/05/msg00002.html
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/GFXJ35WKPME4HYNQCQNAJHLCZOJL2SAE/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/R36OYC5SJ6FLPVAYJYYT4MOJ2I7MGYFF/
- https://openvpn.net/community-downloads/
- https://community.openvpn.net/openvpn/wiki/CVE-2022-0547
- https://community.openvpn.net/openvpn/wiki/SecurityAnnouncements
- https://lists.debian.org/debian-lts-announce/2022/05/msg00002.html
- https://lists.debian.org/debian-lts-announce/2025/03/msg00005.html
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/GFXJ35WKPME4HYNQCQNAJHLCZOJL2SAE/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/R36OYC5SJ6FLPVAYJYYT4MOJ2I7MGYFF/
- https://openvpn.net/community-downloads/
