CVE-2020-7729
📋 TL;DR
CVE-2020-7729 allows arbitrary code execution in Grunt task runner when processing malicious YAML files. The vulnerability exists because Grunt uses the insecure js-yaml load() function instead of safeLoad() to parse YAML files. Anyone using Grunt versions before 1.3.0 to process untrusted YAML files is affected.
💻 Affected Systems
- Grunt task runner
📦 What is this software?
Grunt by Gruntjs
Ubuntu Linux by Canonical
⚠️ Risk & Real-World Impact
Worst Case
Full remote code execution with the privileges of the Grunt process, potentially leading to complete system compromise, data theft, or ransomware deployment.
Likely Case
Local privilege escalation or code execution when developers process malicious YAML files from untrusted sources during build processes.
If Mitigated
Limited impact if only trusted YAML files are processed and proper input validation is implemented.
🎯 Exploit Status
Exploitation requires the victim to process a malicious YAML file. Proof-of-concept exploits are publicly available demonstrating code execution.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 1.3.0 and later
Vendor Advisory: https://github.com/gruntjs/grunt/commit/e350cea1724eb3476464561a380fb6a64e61e4e7
Restart Required: No
Instructions:
1. Update Grunt to version 1.3.0 or later using npm: npm update grunt@latest 2. Verify the update with: npm list grunt 3. Test build processes to ensure compatibility.
🔧 Temporary Workarounds
Input validation and sanitization
allImplement strict validation of YAML file sources and content before processing with Grunt.
Use alternative YAML parser
allReplace grunt.file.readYAML calls with a secure YAML parser like js-yaml with safeLoad().
const yaml = require('js-yaml'); const safeData = yaml.safeLoad(fs.readFileSync('file.yaml', 'utf8'));
🧯 If You Can't Patch
- Restrict YAML file processing to trusted sources only
- Implement network segmentation to isolate build servers from production systems
🔍 How to Verify
Check if Vulnerable:
Check Grunt version: npm list grunt | grep grunt. If version is below 1.3.0, the system is vulnerable.Check Version:
npm list grunt | grep gruntVerify Fix Applied:
After updating, verify with: npm list grunt | grep grunt. Should show version 1.3.0 or higher.📡 Detection & Monitoring
Log Indicators:
- Unusual process execution from Grunt context
- Errors in YAML parsing logs
- Unexpected network connections from build processes
Network Indicators:
- Outbound connections from build servers to unexpected destinations
- DNS requests for command and control domains from CI/CD systems
SIEM Query:
process.name: "node" AND process.args: "grunt" AND event.action: "process_started" AND NOT parent.process.name: "expected_parent_process"🔗 References
- https://github.com/gruntjs/grunt/blob/master/lib/grunt/file.js%23L249
- https://github.com/gruntjs/grunt/commit/e350cea1724eb3476464561a380fb6a64e61e4e7
- https://lists.debian.org/debian-lts-announce/2020/09/msg00008.html
- https://snyk.io/vuln/SNYK-JAVA-ORGWEBJARSNPM-607922
- https://snyk.io/vuln/SNYK-JS-GRUNT-597546
- https://usn.ubuntu.com/4595-1/
- https://github.com/gruntjs/grunt/blob/master/lib/grunt/file.js%23L249
- https://github.com/gruntjs/grunt/commit/e350cea1724eb3476464561a380fb6a64e61e4e7
- https://lists.debian.org/debian-lts-announce/2020/09/msg00008.html
- https://snyk.io/vuln/SNYK-JAVA-ORGWEBJARSNPM-607922
- https://snyk.io/vuln/SNYK-JS-GRUNT-597546
- https://usn.ubuntu.com/4595-1/
