CVE-2025-68972
📋 TL;DR
This GnuPG vulnerability allows attackers to append unauthorized content to signed messages while still passing signature verification. The attack exploits how GnuPG handles formfeed characters (\f) at line endings in signed plaintext. Anyone using GnuPG versions through 2.4.8 for verifying signed messages is potentially affected.
💻 Affected Systems
- GnuPG
- GPG
📦 What is this software?
Gnupg by Gnupg
⚠️ Risk & Real-World Impact
Worst Case
Attackers could modify signed communications (like software updates, contracts, or security advisories) to include malicious content while appearing to have valid signatures, potentially leading to malware installation or fraudulent agreements.
Likely Case
Targeted attacks against organizations relying on GnuPG-signed communications where attackers could append misleading information or malicious links to otherwise legitimate signed messages.
If Mitigated
With proper monitoring and defense-in-depth, the impact is limited as the attack requires specific message manipulation and still produces 'invalid armor' warnings during verification.
🎯 Exploit Status
Proof-of-concept code and detailed analysis are publicly available. Exploitation requires crafting specific messages with formfeed characters but doesn't require authentication to the target system.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: GnuPG 2.4.9 and later
Vendor Advisory: https://dev.gnupg.org/T7247
Restart Required: No
Instructions:
1. Check current GnuPG version: gpg --version
2. Update using your package manager:
- Ubuntu/Debian: sudo apt update && sudo apt upgrade gnupg
- RHEL/CentOS: sudo yum update gnupg
- macOS: brew upgrade gnupg
3. Verify update: gpg --version should show 2.4.9 or higher
🔧 Temporary Workarounds
Reject messages with formfeed characters
allConfigure GnuPG to reject messages containing formfeed (\f) characters during verification
gpg --verify --no-allow-formfeed signed_message.asc
Use armored signature verification only
allOnly verify armored signatures and avoid plaintext verification
gpg --verify signature.asc
🧯 If You Can't Patch
- Implement message validation that strips or rejects formfeed characters before GnuPG processing
- Use alternative signature verification tools for critical communications until patching is possible
🔍 How to Verify
Check if Vulnerable:
Run: gpg --version | head -1. If version is 2.4.8 or earlier, you are vulnerable.Check Version:
gpg --version | head -1Verify Fix Applied:
After updating, verify version is 2.4.9+: gpg --version | head -1📡 Detection & Monitoring
Log Indicators:
- Multiple 'invalid armor' warnings during signature verification
- Unexpected formfeed characters in signed messages
Network Indicators:
- Unusual patterns in signed message transfers
- Messages with appended content after expected signatures
SIEM Query:
gpg_logs WHERE message CONTAINS 'invalid armor' OR message CONTAINS 'formfeed'