CVE-2020-7669
📋 TL;DR
CVE-2020-7669 is a path traversal vulnerability in the tarutil package of u-root that allows attackers to write files outside the intended extraction directory. This affects all versions of the package prior to the fix, potentially enabling arbitrary file overwrite or creation. Any application using this vulnerable package for tar extraction is at risk.
💻 Affected Systems
- github.com/u-root/u-root/pkg/tarutil
📦 What is this software?
U Root by U Root
⚠️ Manual Verification Required
This CVE does not have specific version information in our database, so automatic vulnerability detection cannot determine if your system is affected.
Why? The CVE database entry doesn't specify which versions are vulnerable (no version ranges provided by the vendor/NVD).
🔒 Custom verification scripts are available for registered users. Sign up free to download automated test scripts.
- Review the CVE details at NVD
- Check vendor security advisories for your specific version
- Test if the vulnerability is exploitable in your environment
- Consider updating to the latest version as a precaution
⚠️ Risk & Real-World Impact
Worst Case
Arbitrary file overwrite leading to remote code execution, privilege escalation, or system compromise by writing to critical system files.
Likely Case
Local file overwrite allowing data corruption, denial of service, or limited privilege escalation depending on application context.
If Mitigated
No impact if proper input validation and sandboxing prevent malicious tar files from being processed.
🎯 Exploit Status
Exploitation requires the ability to supply a malicious tar file to the vulnerable application. The vulnerability is well-documented with public proof-of-concept examples.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Fixed in u-root commit 7c8c3c4 and later versions
Vendor Advisory: https://github.com/u-root/u-root/pull/1817
Restart Required: No
Instructions:
1. Update the u-root dependency to version with commit 7c8c3c4 or later. 2. Run 'go get -u github.com/u-root/u-root'. 3. Rebuild and redeploy affected applications.
🔧 Temporary Workarounds
Input validation and sanitization
allValidate and sanitize tar file paths before extraction to prevent path traversal
Implement custom extraction logic that validates all file paths against allowed directories
Sandbox extraction
linuxRun tar extraction in isolated containers or sandboxes with restricted filesystem access
Use Docker containers with read-only root filesystems or chroot jails for extraction
🧯 If You Can't Patch
- Disable tar extraction functionality if not essential
- Implement strict access controls and monitoring on directories where extraction occurs
🔍 How to Verify
Check if Vulnerable:
Check go.mod or vendor dependencies for github.com/u-root/u-root versions before commit 7c8c3c4Check Version:
go list -m github.com/u-root/u-rootVerify Fix Applied:
Verify the u-root dependency includes commit 7c8c3c4 or later in the version history📡 Detection & Monitoring
Log Indicators:
- Unexpected file writes outside extraction directories
- Failed path validation errors
- Tar extraction operations with suspicious file paths
Network Indicators:
- Unusual tar file uploads to applications
- Network transfers of tar files to systems using u-root
SIEM Query:
source="application_logs" AND ("tar extraction" OR "u-root") AND ("path traversal" OR "../" OR "..\\")