CVE-2020-5313
📋 TL;DR
This vulnerability is a buffer overflow in the FLI image decoder component of Pillow (Python Imaging Library). Attackers can exploit this by crafting malicious FLI image files to potentially execute arbitrary code or cause denial of service. Any application using Pillow to process untrusted FLI images is affected.
💻 Affected Systems
- Pillow (Python Imaging Library)
📦 What is this software?
Fedora by Fedoraproject
Fedora by Fedoraproject
Pillow by Python
Ubuntu Linux by Canonical
Ubuntu Linux by Canonical
Ubuntu Linux by Canonical
Ubuntu Linux by Canonical
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to complete system compromise, data theft, or ransomware deployment.
Likely Case
Application crash causing denial of service, potentially leading to data corruption or service disruption.
If Mitigated
Limited impact with proper input validation and sandboxing, potentially just application instability.
🎯 Exploit Status
Buffer overflow vulnerabilities in image parsers are commonly exploited; proof-of-concept code exists in the commit reference.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 6.2.2 and later
Vendor Advisory: https://pillow.readthedocs.io/en/stable/releasenotes/6.2.2.html
Restart Required: No
Instructions:
1. Update Pillow using pip: 'pip install --upgrade Pillow>=6.2.2'. 2. Verify the update with 'pip show Pillow'. 3. Restart any Python applications using Pillow to load the new version.
🔧 Temporary Workarounds
Disable FLI image support
allRemove or disable the FLI image decoder to prevent processing of malicious FLI files.
Modify application code to avoid using Image.open() with FLI files or implement file type validation.
Input validation and sanitization
allImplement strict validation of uploaded image files before processing with Pillow.
Use file magic numbers or libraries like python-magic to verify file types before passing to Pillow.
🧯 If You Can't Patch
- Implement network segmentation to isolate vulnerable systems from untrusted networks.
- Deploy application-level firewalls or WAFs to block malicious image uploads.
🔍 How to Verify
Check if Vulnerable:
Run 'pip show Pillow' and check if version is less than 6.2.2.Check Version:
pip show Pillow | grep VersionVerify Fix Applied:
After updating, run 'pip show Pillow' to confirm version is 6.2.2 or higher.📡 Detection & Monitoring
Log Indicators:
- Application crashes or segmentation faults when processing image files
- Unusual memory usage spikes in Pillow processes
Network Indicators:
- Unexpected uploads of FLI image files to web applications
- Network traffic patterns suggesting image processing exploitation
SIEM Query:
source="application.log" AND ("segmentation fault" OR "buffer overflow" OR "Pillow crash")🔗 References
- https://github.com/python-pillow/Pillow/commit/a09acd0decd8a87ccce939d5ff65dab59e7d365b
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/2MMU3WT2X64GS5WHDPKKC2WZA7UIIQ3A/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/3DUMIBUYGJRAVJCTFUWBRLVQKOUTVX5P/
- https://pillow.readthedocs.io/en/stable/releasenotes/6.2.2.html
- https://usn.ubuntu.com/4272-1/
- https://www.debian.org/security/2020/dsa-4631
- https://github.com/python-pillow/Pillow/commit/a09acd0decd8a87ccce939d5ff65dab59e7d365b
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/2MMU3WT2X64GS5WHDPKKC2WZA7UIIQ3A/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/3DUMIBUYGJRAVJCTFUWBRLVQKOUTVX5P/
- https://pillow.readthedocs.io/en/stable/releasenotes/6.2.2.html
- https://usn.ubuntu.com/4272-1/
- https://www.debian.org/security/2020/dsa-4631
