CVE-2021-3406
📋 TL;DR
CVE-2021-3406 is a critical vulnerability in Keylime versions 5.8.1 and older that breaks the cryptographic chain of trust from hardware endorsement keys to agent attestations. This allows attackers to potentially spoof trusted hardware attestations and bypass security controls. Organizations using Keylime for remote attestation and trusted computing are affected.
💻 Affected Systems
- Keylime
📦 What is this software?
Fedora by Fedoraproject
Keylime by Keylime
⚠️ Risk & Real-World Impact
Worst Case
Attackers could spoof trusted hardware attestations, allowing compromised systems to appear trusted and bypass security controls, potentially leading to full system compromise and data exfiltration.
Likely Case
Unauthorized systems could be registered as trusted, bypassing security policies and gaining access to protected resources or networks.
If Mitigated
With proper network segmentation and monitoring, impact would be limited to the Keylime infrastructure itself rather than broader systems.
🎯 Exploit Status
The vulnerability is in the trust validation logic, making exploitation straightforward once an attacker understands the flaw.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 5.9.0 and later
Vendor Advisory: https://github.com/keylime/keylime/security/advisories/GHSA-78f8-6c68-375m
Restart Required: Yes
Instructions:
1. Update Keylime to version 5.9.0 or later using your package manager. 2. Restart all Keylime services (agent, registrar, verifier). 3. Verify the update was successful.
🔧 Temporary Workarounds
Disable Keylime Services
linuxTemporarily disable Keylime agent and registrar services to prevent exploitation
sudo systemctl stop keylime_agent
sudo systemctl stop keylime_registrar
sudo systemctl disable keylime_agent
sudo systemctl disable keylime_registrar
🧯 If You Can't Patch
- Isolate Keylime infrastructure from production networks using strict firewall rules
- Implement additional monitoring and alerting for unusual attestation patterns
🔍 How to Verify
Check if Vulnerable:
Check Keylime version: 'keylime_agent --version' or 'keylime_registrar --version'. If version is 5.8.1 or older, system is vulnerable.Check Version:
keylime_agent --version && keylime_registrar --versionVerify Fix Applied:
Verify version is 5.9.0 or later and check that services are running properly with 'systemctl status keylime_agent' and 'systemctl status keylime_registrar'.📡 Detection & Monitoring
Log Indicators:
- Unusual attestation patterns
- Multiple failed attestation attempts from same source
- Registrar accepting attestations from previously unknown hardware
Network Indicators:
- Unexpected connections to Keylime ports (8881, 8882, 8883)
- Network traffic patterns inconsistent with normal attestation cycles
SIEM Query:
source="keylime" AND (event="attestation_failure" OR event="untrusted_hardware")🔗 References
- https://bugzilla.redhat.com/show_bug.cgi?id=1932469
- https://github.com/keylime/keylime/security/advisories/GHSA-78f8-6c68-375m
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/YAWKEF2LVXUME266T6RNRVBGAD375QAT/
- https://bugzilla.redhat.com/show_bug.cgi?id=1932469
- https://github.com/keylime/keylime/security/advisories/GHSA-78f8-6c68-375m
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/YAWKEF2LVXUME266T6RNRVBGAD375QAT/
