CVE-2021-33027
📋 TL;DR
Sylabs Singularity Enterprise through version 1.6.2 uses insufficient entropy when generating nonces, making them predictable. This allows attackers to bypass security mechanisms that rely on these nonces. Organizations running affected versions of Singularity Enterprise are vulnerable.
💻 Affected Systems
- Sylabs Singularity Enterprise
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise through predictable nonce exploitation leading to authentication bypass, privilege escalation, or remote code execution.
Likely Case
Authentication bypass or session hijacking allowing unauthorized access to container management systems.
If Mitigated
Limited impact if nonces are only used for non-critical functions or additional authentication layers exist.
🎯 Exploit Status
Predictable nonce vulnerabilities typically have low exploitation complexity once the pattern is identified.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 1.6.3 or later
Vendor Advisory: https://support.sylabs.io/a/solutions/articles/42000086439
Restart Required: Yes
Instructions:
1. Backup current configuration. 2. Upgrade to Singularity Enterprise 1.6.3 or later. 3. Restart all Singularity services. 4. Verify the upgrade was successful.
🔧 Temporary Workarounds
Network Isolation
linuxRestrict network access to Singularity Enterprise to trusted networks only
iptables -A INPUT -p tcp --dport [SINGULARITY_PORT] -s [TRUSTED_NETWORK] -j ACCEPT
iptables -A INPUT -p tcp --dport [SINGULARITY_PORT] -j DROP
🧯 If You Can't Patch
- Implement strict network segmentation to isolate Singularity Enterprise from untrusted networks
- Deploy additional authentication layers and monitor for suspicious authentication attempts
🔍 How to Verify
Check if Vulnerable:
Check Singularity Enterprise version with: singularity versionCheck Version:
singularity versionVerify Fix Applied:
Verify version is 1.6.3 or later and check that nonce generation uses proper entropy sources📡 Detection & Monitoring
Log Indicators:
- Multiple failed authentication attempts followed by successful login
- Unusual nonce patterns or reuse
Network Indicators:
- Unexpected authentication requests from external sources
- Brute force patterns against authentication endpoints
SIEM Query:
source="singularity" AND (event="authentication" OR event="nonce") AND status="success" AND src_ip NOT IN [trusted_ips]