CVE-2021-25287
📋 TL;DR
This vulnerability is an out-of-bounds read in Pillow's JPEG 2000 decoder that could allow attackers to read sensitive data from memory or cause denial of service. It affects applications using Pillow to process JPEG 2000 images. The vulnerability is particularly concerning because it can be triggered by processing malicious image files.
💻 Affected Systems
- Pillow (Python Imaging Library fork)
📦 What is this software?
Fedora by Fedoraproject
Pillow by Python
⚠️ Risk & Real-World Impact
Worst Case
Information disclosure of sensitive memory contents, potential remote code execution through memory corruption, or application crash leading to denial of service.
Likely Case
Application crash (denial of service) when processing malicious JPEG 2000 images, potentially exposing memory contents.
If Mitigated
No impact if vulnerable code is not used or if proper input validation/sandboxing prevents malicious image processing.
🎯 Exploit Status
Exploitation requires only a malicious JPEG 2000 image file. The vulnerability is in image parsing code, making it easy to trigger.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 8.2.0 and later
Vendor Advisory: https://pillow.readthedocs.io/en/stable/releasenotes/8.2.0.html#cve-2021-25287-cve-2021-25288-fix-oob-read-in-jpeg2kdecode
Restart Required: No
Instructions:
1. Update Pillow: pip install --upgrade pillow>=8.2.0
2. Verify installation: pip show pillow
3. Test with sample JPEG 2000 images to ensure functionality
🔧 Temporary Workarounds
Disable JPEG 2000 support
allRemove or disable JPEG 2000 image processing functionality in your application
# Modify application code to reject JPEG 2000 files or use alternative image formats
Input validation and sanitization
allValidate and sanitize image uploads before processing
# Implement file type validation and size limits for image uploads
🧯 If You Can't Patch
- Implement strict input validation for image uploads - reject JPEG 2000 files entirely
- Run vulnerable applications in sandboxed/isolated environments with minimal privileges
🔍 How to Verify
Check if Vulnerable:
Check Pillow version: python -c "import PIL; print(PIL.__version__)" and compare to 8.2.0Check Version:
python -c "import PIL; print('Pillow version:', PIL.__version__)"Verify Fix Applied:
Verify Pillow version is 8.2.0 or higher and test with known safe JPEG 2000 images📡 Detection & Monitoring
Log Indicators:
- Application crashes or segmentation faults when processing images
- Unusual memory access patterns in application logs
- Failed image processing operations
Network Indicators:
- Uploads of JPEG 2000 files to web applications
- Unusual spikes in image upload traffic
SIEM Query:
source="application.logs" AND ("segmentation fault" OR "memory error" OR "PIL crash") AND "image"🔗 References
- https://github.com/python-pillow/Pillow/pull/5377#issuecomment-833821470
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/MQHA5HAIBOYI3R6HDWCLAGFTIQP767FL/
- https://pillow.readthedocs.io/en/stable/releasenotes/8.2.0.html#cve-2021-25287-cve-2021-25288-fix-oob-read-in-jpeg2kdecode
- https://security.gentoo.org/glsa/202107-33
- https://github.com/python-pillow/Pillow/pull/5377#issuecomment-833821470
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/MQHA5HAIBOYI3R6HDWCLAGFTIQP767FL/
- https://pillow.readthedocs.io/en/stable/releasenotes/8.2.0.html#cve-2021-25287-cve-2021-25288-fix-oob-read-in-jpeg2kdecode
- https://security.gentoo.org/glsa/202107-33
