CVE-2025-68131
📋 TL;DR
This vulnerability in the cbor2 library allows attackers to read sensitive data from previously decoded CBOR messages when a CBORDecoder instance is reused across multiple decode operations. It affects applications that process untrusted CBOR data using cbor2 versions 3.0.0 through 5.7.0. The issue enables information disclosure across trust boundaries.
💻 Affected Systems
- cbor2 Python library
📦 What is this software?
Cbor2 by Agronholm
⚠️ Risk & Real-World Impact
Worst Case
Complete disclosure of sensitive data from previous CBOR messages, potentially including authentication tokens, personal information, or cryptographic keys.
Likely Case
Partial information leakage from previously processed CBOR data, potentially exposing user data or application state.
If Mitigated
No data leakage if decoder instances are not reused across trust boundaries or proper version is used.
🎯 Exploit Status
Exploitation requires the attacker to control CBOR input and the decoder must be reused. The vulnerability is well-documented in the advisory.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 5.8.0
Vendor Advisory: https://github.com/agronholm/cbor2/security/advisories/GHSA-wcj4-jw5j-44wh
Restart Required: No
Instructions:
1. Update cbor2 to version 5.8.0 or later using pip: pip install --upgrade cbor2>=5.8.0
2. Verify the update with: pip show cbor2
3. No application restart required for Python library updates.
🔧 Temporary Workarounds
Avoid decoder reuse
allCreate new CBORDecoder instances for each decode operation instead of reusing them, especially when processing untrusted data.
Isolate trusted/untrusted decoders
allUse separate decoder instances for trusted and untrusted CBOR data sources.
🧯 If You Can't Patch
- Implement strict input validation and sanitization for all CBOR data
- Isolate CBOR processing to dedicated, ephemeral processes or containers
🔍 How to Verify
Check if Vulnerable:
Check cbor2 version with: python -c "import cbor2; print(cbor2.__version__)" and verify if between 3.0.0 and 5.7.0 inclusive.Check Version:
python -c "import cbor2; print(cbor2.__version__)"Verify Fix Applied:
Verify version is 5.8.0 or higher with: python -c "import cbor2; print(cbor2.__version__)"📡 Detection & Monitoring
Log Indicators:
- Unusual CBOR processing errors
- Memory access patterns in CBOR decoding
Network Indicators:
- Unexpected CBOR data patterns or sizes
- Repeated CBOR decode operations from same source
SIEM Query:
Process monitoring for cbor2 library usage with version checks