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How the CVE Works:
CVE-2025-3757 exploits a flaw in OpenPubkey’s JWS (JSON Web Signature) verification process. Attackers can craft a malicious JWS token with manipulated headers or payloads that bypass signature validation. The library fails to enforce proper cryptographic checks, allowing unverified tokens to be accepted as authentic. This occurs due to improper handling of key binding and weak enforcement of signature algorithms. The vulnerability enables unauthorized access to systems relying on OpenPubkey for authentication.
DailyCVE Form:
Platform: OpenPubkey
Version: <0.10.0
Vulnerability: Auth Bypass
Severity: Critical
Date: May 13, 2025
What Undercode Say:
Exploitation:
- Craft a JWS token with a tampered payload:
echo '{"alg":"none","kid":"malicious"}' | base64
2. Combine with a fake signature:
echo -n "header.payload." | openssl dgst -sha256 -binary | base64
3. Send the token to bypass auth:
curl -H "Authorization: Bearer <malicious_token>" http://target/login
Protection:
1. Upgrade OpenPubkey:
pip install openpubkey>=0.10.0
2. Enforce strict JWS validation:
from openpubkey import verify_jws verify_jws(token, strict_algs=["RS256", "ES256"])
3. Monitor logs for invalid tokens:
grep "Invalid JWS" /var/log/auth.log
Analytics:
- Attack Vector: Network
- Complexity: Low
- Privileges Required: None
- User Interaction: None
Detection:
1. Scan for vulnerable versions:
pip list | grep "openpubkey"
2. Check for unverified tokens in apps:
if token_unverified:
raise Exception("CVE-2025-3757 detected!")
Mitigation:
- Revoke all existing tokens post-upgrade.
- Implement rate-limiting on auth endpoints.
- Use HSM-backed keys for JWS signing.
No further commentary.
Sources:
Reported By: github.com
Extra Source Hub:
Undercode
