CVE-2023-6258
📋 TL;DR
This vulnerability in pkcs11-provider allows a Bleichenbacher-like side-channel attack against PKCS#1 1.5 decryption. Attackers could potentially decrypt sensitive data or forge signatures by analyzing timing differences during cryptographic operations. Systems using pkcs11-provider for PKCS#1 1.5 RSA decryption are affected.
💻 Affected Systems
- pkcs11-provider
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete compromise of encrypted communications, decryption of sensitive data, or signature forgery leading to authentication bypass.
Likely Case
Partial information leakage about encrypted data through timing analysis, potentially enabling decryption of targeted messages over multiple attempts.
If Mitigated
Minimal impact if systems use RSA-OAEP instead of PKCS#1 1.5 or have patched the vulnerability.
🎯 Exploit Status
Exploitation requires precise timing measurements and multiple attempts, making it complex but feasible for determined attackers with network access.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Fixed in commit from PR #308 (specific version numbers may vary by distribution)
Vendor Advisory: https://bugzilla.redhat.com/show_bug.cgi?id=2251062
Restart Required: Yes
Instructions:
1. Update pkcs11-provider package from your distribution's repository. 2. Restart services using pkcs11-provider. 3. For source installations: pull latest code from GitHub and rebuild.
🔧 Temporary Workarounds
Disable PKCS#1 1.5 RSA decryption
linuxConfigure applications to use RSA-OAEP instead of PKCS#1 1.5 for RSA decryption operations.
# Configure application-specific settings to use RSA-OAEP
Network segmentation
linuxRestrict network access to services using pkcs11-provider to trusted networks only.
# Use firewall rules: iptables -A INPUT -p tcp --dport <service_port> -s <trusted_network> -j ACCEPT
# iptables -A INPUT -p tcp --dport <service_port> -j DROP
🧯 If You Can't Patch
- Implement strict network access controls to limit exposure to trusted sources only.
- Monitor for unusual timing patterns or repeated failed decryption attempts in logs.
🔍 How to Verify
Check if Vulnerable:
Check pkcs11-provider version: rpm -q pkcs11-provider or dpkg -l | grep pkcs11-provider. If version predates fix in PR #308, system is vulnerable.Check Version:
rpm -q pkcs11-provider # RHEL/CentOS/Fedora
dpkg -l | grep pkcs11-provider # Debian/UbuntuVerify Fix Applied:
Verify updated version is installed and check that services using pkcs11-provider are restarted.📡 Detection & Monitoring
Log Indicators:
- Multiple failed decryption attempts with similar timing patterns
- Unusual volume of PKCS#1 1.5 decryption requests
Network Indicators:
- Repeated connections to services using pkcs11-provider with crafted payloads
- Unusual timing patterns in network traffic
SIEM Query:
source="*pkcs11*" AND (event_type="decryption_failed" OR event_type="timing_anomaly") | stats count by src_ip