CVE-2021-45911
📋 TL;DR
CVE-2021-45911 is a heap-based buffer overflow vulnerability in gif2apng 1.9 that allows attackers to write 2 bytes outside buffer boundaries. This affects systems running the vulnerable gif2apng version, potentially allowing arbitrary code execution or application crashes. Users who process GIF files with gif2apng are at risk.
💻 Affected Systems
- gif2apng
📦 What is this software?
Gif2apng by Gif2apng Project
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to complete system compromise if gif2apng processes malicious GIF files from untrusted sources.
Likely Case
Application crash (denial of service) when processing specially crafted GIF files.
If Mitigated
Limited impact if gif2apng only processes trusted GIF files with proper input validation.
🎯 Exploit Status
Exploitation requires providing a malicious GIF file to gif2apng. The vulnerability is in the main function and can be triggered during normal conversion operations.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Version 1.9-1 (Debian patched version)
Vendor Advisory: https://lists.debian.org/debian-lts-announce/2022/03/msg00008.html
Restart Required: No
Instructions:
1. Update gif2apng package using your distribution's package manager. 2. For Debian/Ubuntu: sudo apt update && sudo apt install gif2apng. 3. Verify installation with: gif2apng --version
🔧 Temporary Workarounds
Disable gif2apng usage
linuxRemove or restrict execution of gif2apng binary
sudo chmod 000 /usr/bin/gif2apng
sudo mv /usr/bin/gif2apng /usr/bin/gif2apng.disabled
Input validation
allOnly allow trusted GIF files to be processed by gif2apng
🧯 If You Can't Patch
- Remove gif2apng from production systems
- Use alternative GIF to APNG conversion tools like ImageMagick
🔍 How to Verify
Check if Vulnerable:
Check gif2apng version: gif2apng --version | grep '1.9$'Check Version:
gif2apng --versionVerify Fix Applied:
Verify version is not 1.9: gif2apng --version | grep -v '1.9$'📡 Detection & Monitoring
Log Indicators:
- Segmentation fault or crash logs from gif2apng process
- Unexpected termination of gif2apng conversion jobs
Network Indicators:
- N/A - Local file processing vulnerability
SIEM Query:
process.name:"gif2apng" AND (event.action:"segmentation_fault" OR event.outcome:"failure")