CVE-2019-7537
📋 TL;DR
CVE-2019-7537 is a critical remote code execution vulnerability in Donfig 0.3.0 that allows attackers to execute arbitrary Python commands through the collect_yaml method. This affects any system using the vulnerable Donfig library to process YAML configuration files. Attackers can gain complete control of affected systems.
💻 Affected Systems
- Donfig
📦 What is this software?
Donfig by Pytroll
⚠️ Risk & Real-World Impact
Worst Case
Full system compromise with attacker gaining root/admin privileges, data exfiltration, ransomware deployment, and persistent backdoor installation.
Likely Case
Unauthorized code execution leading to data theft, lateral movement within the network, and cryptocurrency mining malware installation.
If Mitigated
Limited impact with proper network segmentation, minimal privileges, and input validation preventing successful exploitation.
🎯 Exploit Status
The vulnerability is straightforward to exploit as it involves passing malicious YAML content to the collect_yaml method. Public proof-of-concept code exists in GitHub issues.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Versions after 0.3.0 (0.3.1 and later)
Vendor Advisory: https://github.com/pytroll/donfig/issues/5
Restart Required: No
Instructions:
1. Upgrade Donfig to version 0.3.1 or later using pip: pip install --upgrade donfig
2. Verify the upgrade with: pip show donfig
3. Test that YAML parsing functionality still works correctly in your application.
🔧 Temporary Workarounds
Disable YAML parsing
allModify code to avoid using the vulnerable collect_yaml method
# Replace vulnerable YAML parsing with safe alternatives
# Example: Use json.loads() instead of yaml.safe_load()
# Remove or comment out calls to collect_yaml() in config_obj.py
Input validation and sanitization
allImplement strict validation of YAML input before processing
# Add input validation before calling collect_yaml
import re
# Validate YAML contains only safe characters
def validate_yaml(yaml_content):
if re.search(r'[!@#$%^&*()_+\[\]{};:\"'<>?/\\|`~]', yaml_content):
raise ValueError('Invalid YAML content')
🧯 If You Can't Patch
- Implement network segmentation to isolate systems using Donfig from untrusted networks
- Deploy application-level firewalls to monitor and block suspicious YAML payloads
🔍 How to Verify
Check if Vulnerable:
Check Donfig version with: python -c "import donfig; print(donfig.__version__)" - if output is '0.3.0', the system is vulnerable.Check Version:
python -c "import donfig; print(donfig.__version__)"Verify Fix Applied:
After upgrading, verify version is 0.3.1 or later with same command. Test YAML parsing functionality to ensure it works without executing arbitrary code.📡 Detection & Monitoring
Log Indicators:
- Unusual Python process execution from YAML parsing functions
- Errors in application logs related to YAML parsing failures
- Suspicious import statements in YAML files
Network Indicators:
- Unusual outbound connections from systems processing YAML files
- Traffic patterns indicating data exfiltration after YAML processing
SIEM Query:
source="application.logs" AND "collect_yaml" AND ("os.system" OR "subprocess" OR "exec" OR "eval")