CVE-2020-12658
📋 TL;DR
CVE-2020-12658 is a critical vulnerability in gssproxy (GSS-API proxy daemon) where improper mutex handling during shutdown can cause denial of service. The flaw allows an attacker to crash the gssproxy service, potentially disrupting authentication services that rely on it. Systems using gssproxy versions before 0.8.3 for GSS-API authentication are affected.
💻 Affected Systems
- gssproxy
- gss-proxy
📦 What is this software?
Gssproxy by Gssproxy Project
⚠️ Risk & Real-World Impact
Worst Case
Complete denial of service for all GSS-API authentication services, potentially disrupting system authentication and causing system instability.
Likely Case
Service crash leading to temporary authentication failures until service restart.
If Mitigated
Minimal impact if gssproxy is not critical for authentication or if redundant authentication mechanisms exist.
🎯 Exploit Status
The vulnerability is triggered during shutdown, making exploitation timing-dependent. Upstream maintainers question the practical exploitability.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 0.8.3 and later
Vendor Advisory: https://pagure.io/gssproxy/c/cb761412e299ef907f22cd7c4146d50c8a792003?branch=master
Restart Required: Yes
Instructions:
1. Update gssproxy to version 0.8.3 or later using your distribution's package manager. 2. For RHEL/CentOS: 'yum update gssproxy'. 3. For Debian/Ubuntu: 'apt-get update && apt-get install gssproxy'. 4. Restart the gssproxy service: 'systemctl restart gssproxy'.
🔧 Temporary Workarounds
Disable gssproxy if not needed
linuxStop and disable the gssproxy service if your system doesn't require GSS-API authentication proxying.
systemctl stop gssproxy
systemctl disable gssproxy
Implement service monitoring and auto-restart
linuxConfigure monitoring to automatically restart gssproxy if it crashes.
systemctl edit gssproxy
Add: Restart=always under [Service] section
🧯 If You Can't Patch
- Implement strict network controls to limit access to gssproxy service
- Monitor gssproxy process health and implement alerting for service crashes
🔍 How to Verify
Check if Vulnerable:
Check gssproxy version: 'gssproxy --version' or 'rpm -q gssproxy' or 'dpkg -l | grep gssproxy'Check Version:
gssproxy --version 2>/dev/null || rpm -q gssproxy 2>/dev/null || dpkg -l | grep gssproxyVerify Fix Applied:
Verify version is 0.8.3 or higher: 'gssproxy --version' should show 0.8.3+📡 Detection & Monitoring
Log Indicators:
- gssproxy service crash logs in systemd journal: 'journalctl -u gssproxy --since "1 hour ago"'
- Segmentation fault or abnormal termination messages in /var/log/messages
Network Indicators:
- Failed GSS-API authentication attempts
- Unresponsive authentication services
SIEM Query:
source="systemd" AND program="gssproxy" AND ("segmentation fault" OR "crash" OR "terminated")🔗 References
- https://github.com/gssapi/gssproxy/commit/cb761412e299ef907f22cd7c4146d50c8a792003
- https://github.com/gssapi/gssproxy/compare/v0.8.2...v0.8.3
- https://lists.debian.org/debian-lts-announce/2021/01/msg00004.html
- https://pagure.io/gssproxy/c/cb761412e299ef907f22cd7c4146d50c8a792003?branch=master
- https://github.com/gssapi/gssproxy/commit/cb761412e299ef907f22cd7c4146d50c8a792003
- https://github.com/gssapi/gssproxy/compare/v0.8.2...v0.8.3
- https://lists.debian.org/debian-lts-announce/2021/01/msg00004.html
- https://pagure.io/gssproxy/c/cb761412e299ef907f22cd7c4146d50c8a792003?branch=master
