CVE-2023-5342
📋 TL;DR
An expired Fedora Secure Boot CA certificate in shim could allow loading of old or invalid signed boot components, potentially bypassing Secure Boot protections. This affects Fedora systems using the vulnerable shim package. The vulnerability requires physical or administrative access to exploit.
💻 Affected Systems
- Fedora shim package
⚠️ 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
An attacker with physical access could load malicious boot components, potentially gaining persistent system control and bypassing Secure Boot entirely.
Likely Case
Accidental loading of outdated but legitimate boot components, causing boot failures or system instability.
If Mitigated
Minimal impact if Secure Boot is disabled or if alternative boot verification mechanisms are in place.
🎯 Exploit Status
Exploitation requires physical access or administrative privileges to modify boot configuration.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: shim-15.8-2 or later
Vendor Advisory: https://access.redhat.com/security/cve/CVE-2023-5342
Restart Required: No
Instructions:
1. Update shim package: sudo dnf update shim 2. Verify update: rpm -q shim 3. Regenerate initramfs if needed: sudo dracut --force
🔧 Temporary Workarounds
Disable Secure Boot
allTemporarily disable Secure Boot in BIOS/UEFI settings to prevent certificate validation issues
🧯 If You Can't Patch
- Monitor boot logs for unexpected certificate validation failures
- Implement physical security controls to prevent unauthorized system access
🔍 How to Verify
Check if Vulnerable:
Check shim version: rpm -q shim | grep -E 'shim-15\.(4|6|7)'Check Version:
rpm -q shimVerify Fix Applied:
Verify shim version is 15.8-2 or later: rpm -q shim📡 Detection & Monitoring
Log Indicators:
- Secure Boot validation failures in dmesg or journalctl
- Unexpected boot component loading messages
Network Indicators:
- None - local exploit only
SIEM Query:
source="dmesg" AND "Secure Boot" AND ("certificate expired" OR "validation failed")