CVE-2020-13388
📋 TL;DR
This vulnerability in the jw.util Python package allows remote code execution when loading YAML configurations. Attackers can execute arbitrary Python code leading to OS command execution by exploiting unsafe YAML loading functions. Any Python application using jw.util versions before 2.3 with YAML configuration loading is affected.
💻 Affected Systems
- jw.util Python package
📦 What is this software?
Jw.util by Python
⚠️ Risk & Real-World Impact
Worst Case
Full system compromise with attacker gaining remote shell access, data exfiltration, and lateral movement within the network.
Likely Case
Arbitrary command execution on the vulnerable system, potentially leading to data theft, service disruption, or installation of malware.
If Mitigated
Limited impact with proper network segmentation, minimal privileges, and input validation preventing exploitation.
🎯 Exploit Status
Exploitation requires the application to process attacker-controlled YAML input through vulnerable functions.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 2.3 and later
Vendor Advisory: https://joel-malwarebenchmark.github.io/blog/2020/04/27/cve-2020-13388-jw-util-vulnerability/
Restart Required: No
Instructions:
1. Update jw.util package to version 2.3 or later using pip: pip install --upgrade jw.util>=2.3
2. Verify the update was successful
3. Test application functionality after update
🔧 Temporary Workarounds
Replace unsafe YAML loading
allManually replace FromString/FromStream calls with safe YAML loading methods
Replace yaml.load() with yaml.safe_load() in affected code
Input validation and sanitization
allImplement strict input validation for YAML configuration sources
🧯 If You Can't Patch
- Implement strict network controls to limit access to vulnerable services
- Apply principle of least privilege to application service accounts
🔍 How to Verify
Check if Vulnerable:
Check Python environment for jw.util version: python -c "import jw.util; print(jw.util.__version__)"Check Version:
pip show jw.util | grep VersionVerify Fix Applied:
Verify installed version is 2.3 or higher and check code for safe YAML loading usage📡 Detection & Monitoring
Log Indicators:
- Unusual Python process execution patterns
- Suspicious YAML parsing errors
- Unexpected system command execution
Network Indicators:
- Unusual outbound connections from application servers
- Traffic to unexpected ports from Python processes
SIEM Query:
source="application.logs" AND ("FromString" OR "FromStream") AND "YAML" AND status="error"🔗 References
- https://joel-malwarebenchmark.github.io
- https://joel-malwarebenchmark.github.io/blog/2020/04/27/cve-2020-13388-jw-util-vulnerability/
- https://security.netapp.com/advisory/ntap-20200528-0002/
- https://joel-malwarebenchmark.github.io
- https://joel-malwarebenchmark.github.io/blog/2020/04/27/cve-2020-13388-jw-util-vulnerability/
- https://security.netapp.com/advisory/ntap-20200528-0002/
