CVE-2021-41131
📋 TL;DR
This path traversal vulnerability in python-tuf allows attackers to overwrite .json files anywhere on the client system by using path traversal characters in rolenames. It affects implementations that allow arbitrary rolename selection for delegated targets metadata. The impact is limited since attackers need to insert signed metadata and the written content must be valid targets files.
💻 Affected Systems
- python-tuf (Python reference implementation of The Update Framework)
📦 What is this software?
The Update Framework by Linuxfoundation
⚠️ Risk & Real-World Impact
Worst Case
Arbitrary .json file overwrite anywhere on the client system, potentially leading to system compromise or data loss.
Likely Case
Limited file overwrite in specific directories where the client has write permissions, potentially disrupting application functionality.
If Mitigated
No impact if rolenames are restricted or metadata storage uses non-vulnerable naming schemes.
🎯 Exploit Status
Exploitation requires: 1) Ability to insert new metadata for path-traversing role, 2) Get the role delegated by existing targets metadata, 3) Provide valid signed targets file content.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 0.19 or newer
Vendor Advisory: https://github.com/theupdateframework/python-tuf/security/advisories/GHSA-wjw6-2cqr-j4qr
Restart Required: Yes
Instructions:
1. Upgrade python-tuf to version 0.19 or newer using pip: 'pip install python-tuf>=0.19'. 2. Restart any services using python-tuf. 3. Verify the update was successful.
🧯 If You Can't Patch
- Restrict allowed character set for rolenames in your implementation
- Implement custom metadata storage with non-vulnerable file naming
🔍 How to Verify
Check if Vulnerable:
Check python-tuf version: 'pip show python-tuf' or 'python -c "import tuf; print(tuf.__version__)"' - if version < 0.19, you are vulnerable.Check Version:
python -c "import tuf; print(tuf.__version__)"Verify Fix Applied:
After upgrading, verify version is 0.19 or newer using same commands.📡 Detection & Monitoring
Log Indicators:
- Unusual file write operations to .json files outside expected metadata directories
- Path traversal patterns in rolename parameters
Network Indicators:
- Unusual metadata requests with path traversal characters in rolenames
SIEM Query:
Search for file write events to .json files with path traversal patterns (e.g., '..' or '../') in file paths from python-tuf processes.🔗 References
- https://github.com/theupdateframework/python-tuf/commit/4ad7ae48fda594b640139c3b7eae21ed5155a102
- https://github.com/theupdateframework/python-tuf/issues/1527
- https://github.com/theupdateframework/python-tuf/security/advisories/GHSA-wjw6-2cqr-j4qr
- https://github.com/theupdateframework/python-tuf/commit/4ad7ae48fda594b640139c3b7eae21ed5155a102
- https://github.com/theupdateframework/python-tuf/issues/1527
- https://github.com/theupdateframework/python-tuf/security/advisories/GHSA-wjw6-2cqr-j4qr
