CVE-2020-15904
📋 TL;DR
CVE-2020-15904 is a heap buffer overflow vulnerability in bsdiff4's patching routine that allows attackers to write beyond allocated memory bounds via a malicious patch file. This affects all applications using bsdiff4 for binary patching operations. Attackers could potentially execute arbitrary code or crash applications processing crafted patches.
💻 Affected Systems
- bsdiff4 Python library
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to complete system compromise if the vulnerable application processes attacker-controlled patch files with elevated privileges.
Likely Case
Application crash (denial of service) when processing malformed patch files, potentially disrupting patching or update processes.
If Mitigated
Limited impact if patch files come from trusted sources only and applications run with minimal privileges.
🎯 Exploit Status
Exploitation requires the target to process a malicious patch file. The vulnerability is in the core patching logic, making reliable exploitation feasible.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 1.2.0 and later
Vendor Advisory: https://github.com/ilanschnell/bsdiff4/blob/master/CHANGELOG.txt
Restart Required: No
Instructions:
1. Update bsdiff4 using pip: 'pip install --upgrade bsdiff4>=1.2.0' 2. Verify the update with: 'pip show bsdiff4' 3. Restart any applications using bsdiff4 to load the updated library.
🔧 Temporary Workarounds
Validate patch file sources
allOnly accept patch files from trusted, authenticated sources with integrity verification.
Sandbox patching operations
allRun bsdiff4 operations in isolated containers or with minimal privileges.
🧯 If You Can't Patch
- Implement strict input validation for patch files before processing
- Run applications using bsdiff4 with reduced privileges and in isolated environments
🔍 How to Verify
Check if Vulnerable:
Check bsdiff4 version with: 'python -c "import bsdiff4; print(bsdiff4.__version__)"' or 'pip show bsdiff4 | grep Version'Check Version:
python -c "import bsdiff4; print(bsdiff4.__version__)"Verify Fix Applied:
Confirm version is 1.2.0 or higher using the version check command.📡 Detection & Monitoring
Log Indicators:
- Application crashes during patch processing
- Memory access violation errors in application logs
- Unexpected process termination during patching operations
Network Indicators:
- Unusual patch file downloads from untrusted sources
- Large or malformed patch files being transferred
SIEM Query:
Process termination events from applications known to use bsdiff4 OR File transfer events containing .patch files followed by application crashes🔗 References
- https://github.com/ilanschnell/bsdiff4/blob/master/CHANGELOG.txt
- https://github.com/ilanschnell/bsdiff4/commit/49a4cee2feef7deaf9d89e5e793a8824930284d7
- https://github.com/ilanschnell/bsdiff4/blob/master/CHANGELOG.txt
- https://github.com/ilanschnell/bsdiff4/commit/49a4cee2feef7deaf9d89e5e793a8824930284d7
