CVE-2021-45972
📋 TL;DR
CVE-2021-45972 is a stack-based buffer overflow vulnerability in giftrans 1.12.2's giftrans function, where attacker-controlled input determines how much data gets written. This allows attackers to overwrite up to 250 bytes beyond the allocated buffer with arbitrary data, potentially leading to arbitrary code execution. Anyone using giftrans 1.12.2 to process GIF files from untrusted sources is affected.
💻 Affected Systems
- giftrans
📦 What is this software?
Giftrans by Giftrans Project
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution with the privileges of the giftrans process, potentially leading to full system compromise if running with elevated privileges.
Likely Case
Application crash (denial of service) or limited memory corruption leading to unpredictable behavior.
If Mitigated
Controlled crash with no code execution if modern exploit mitigations (ASLR, stack canaries) are effective.
🎯 Exploit Status
Exploitation requires crafting a malicious GIF file and getting it processed by giftrans. No public exploit code has been documented.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 1.12.3 or later
Vendor Advisory: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1002739
Restart Required: No
Instructions:
1. Check current version: giftrans --version
2. Update via package manager: sudo apt update && sudo apt upgrade giftrans
3. Verify update: giftrans --version should show 1.12.3 or higher
🔧 Temporary Workarounds
Input validation wrapper
linuxCreate a wrapper script that validates GIF files before passing to giftrans
#!/bin/bash
# Validate file is actually a GIF before processing
if file "$1" | grep -q "GIF image"; then
giftrans "$1"
else
echo "Invalid file type"
exit 1
fi
Disable giftrans usage
linuxRemove or restrict execution permissions for giftrans binary
sudo chmod 000 /usr/bin/giftrans
sudo mv /usr/bin/giftrans /usr/bin/giftrans.disabled
🧯 If You Can't Patch
- Replace giftrans with alternative GIF processing tools like ImageMagick or GraphicsMagick
- Run giftrans in a sandboxed/containerized environment with minimal privileges
🔍 How to Verify
Check if Vulnerable:
Run: giftrans --version | grep -q '1.12.2' && echo 'VULNERABLE' || echo 'NOT VULNERABLE'Check Version:
giftrans --versionVerify Fix Applied:
Run: giftrans --version | grep -q '1.12.3' && echo 'PATCHED' || echo 'STILL VULNERABLE'📡 Detection & Monitoring
Log Indicators:
- Segmentation fault or crash logs from giftrans process
- Unexpected process termination with signal 11 (SIGSEGV)
Network Indicators:
- Unusual GIF file uploads to systems known to use giftrans
- Multiple failed giftrans executions in short time
SIEM Query:
process_name:"giftrans" AND (event_type:"crash" OR exit_code:139)🔗 References
- http://web.archive.org/web/20150801185019/
- https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1002739
- https://www.abdn.ac.uk/tools/ibmpc/giftrans/index.hti
- http://web.archive.org/web/20150801185019/
- https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1002739
- https://www.abdn.ac.uk/tools/ibmpc/giftrans/index.hti
