CVE-2025-62291
📋 TL;DR
This vulnerability in strongSwan's eap-mschapv2 plugin allows a malicious EAP-MSCHAPv2 server to trigger an integer underflow and heap-based buffer overflow by sending specially crafted small messages. Attackers could potentially execute arbitrary code or cause denial of service on vulnerable strongSwan clients. This affects strongSwan clients configured to use EAP-MSCHAPv2 authentication.
💻 Affected Systems
- strongSwan
⚠️ Manual Verification Required
This CVE does not have specific version information in our database, so automatic vulnerability detection cannot determine if your system is affected.
Why? The CVE database entry doesn't specify which versions are vulnerable (no version ranges provided by the vendor/NVD).
🔒 Custom verification scripts are available for registered users. Sign up free to download automated test scripts.
- Review the CVE details at NVD
- Check vendor security advisories for your specific version
- Test if the vulnerability is exploitable in your environment
- Consider updating to the latest version as a precaution
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution on vulnerable strongSwan clients, potentially leading to full system compromise.
Likely Case
Denial of service (crash) of the strongSwan client process, disrupting VPN connectivity.
If Mitigated
Limited impact if strongSwan is not configured to use EAP-MSCHAPv2 or if network segmentation prevents access to malicious servers.
🎯 Exploit Status
Exploitation requires the attacker to control an EAP-MSCHAPv2 server that the victim connects to.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 6.0.3
Vendor Advisory: https://www.strongswan.org/blog/2025/10/27/strongswan-vulnerability-%28cve-2025-62291%29.html
Restart Required: Yes
Instructions:
1. Download strongSwan 6.0.3 or later from https://www.strongswan.org/download.html
2. Follow installation instructions for your platform
3. Restart strongSwan services
🔧 Temporary Workarounds
Disable EAP-MSCHAPv2
linuxRemove or disable EAP-MSCHAPv2 authentication method from strongSwan client configuration
# Edit strongSwan configuration (typically /etc/ipsec.conf or /etc/strongswan.conf)
# Remove or comment out any 'eap-mschapv2' references in authentication methods
🧯 If You Can't Patch
- Implement network segmentation to restrict which EAP servers clients can connect to
- Monitor for unusual authentication attempts or crashes in strongSwan client logs
🔍 How to Verify
Check if Vulnerable:
Check strongSwan version and configuration for EAP-MSCHAPv2 usageCheck Version:
strongswan --versionVerify Fix Applied:
Verify strongSwan version is 6.0.3 or later and EAP-MSCHAPv2 is either disabled or patched📡 Detection & Monitoring
Log Indicators:
- strongSwan client crashes
- Authentication failures with EAP-MSCHAPv2
- Memory corruption errors in system logs
Network Indicators:
- Unusual EAP-MSCHAPv2 authentication attempts
- Small (6-8 byte) EAP-MSCHAPv2 messages
SIEM Query:
source="strongswan" AND (event="crash" OR event="segmentation fault" OR message="*eap-mschapv2*")🔗 References
- https://github.com/strongswan/strongswan/commits/master/src/libcharon/plugins/eap_mschapv2
- https://github.com/strongswan/strongswan/releases
- https://www.strongswan.org/blog/2025/10/27/strongswan-vulnerability-%28cve-2025-62291%29.html
- https://lists.debian.org/debian-lts-announce/2025/11/msg00002.html
