CVE-2025-45765
📋 TL;DR
CVE-2025-45765 is a weak encryption vulnerability in ruby-jwt v3.0.0.beta1 that allows attackers to potentially forge or tamper with JWT tokens due to insufficient key size enforcement. This affects applications using this specific beta version of the ruby-jwt library for JWT token generation or validation. The vulnerability stems from the library not enforcing minimum key sizes, relying instead on underlying OpenSSL restrictions.
💻 Affected Systems
- ruby-jwt
⚠️ 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
Attackers could forge valid JWT tokens, bypass authentication entirely, impersonate users, escalate privileges, or tamper with session data in applications relying on JWT for security.
Likely Case
Authentication bypass in applications using weak keys, potentially allowing unauthorized access to protected resources or functionality.
If Mitigated
Limited impact if applications already use strong keys or have additional authentication layers, though weak keys remain vulnerable.
🎯 Exploit Status
Exploitation requires knowledge of weak keys or ability to generate them; public proof-of-concept exists in the GitHub issue.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: v3.0.0.beta2 or later, or use stable versions like v2.7.1
Vendor Advisory: https://github.com/jwt/ruby-jwt/issues/668
Restart Required: Yes
Instructions:
1. Update ruby-jwt gem: `gem update jwt` or specify version in Gemfile. 2. Restart the Ruby application or server. 3. Verify the update with `gem list jwt`.
🔧 Temporary Workarounds
Enforce key size validation manually
allAdd custom validation in application code to reject keys below minimum size (e.g., 2048 bits for RSA).
# In Ruby code, check key size before using JWT
# Example for RSA keys: key.n.num_bits >= 2048
Use strong keys only
allEnsure all JWT keys meet modern security standards (e.g., RSA 2048+ bits, ECDSA with appropriate curves).
# Generate strong keys: openssl genrsa -out private.pem 2048
🧯 If You Can't Patch
- Monitor for unusual authentication attempts or token usage in logs.
- Implement additional authentication factors or rate limiting to reduce risk.
🔍 How to Verify
Check if Vulnerable:
Check ruby-jwt version with `gem list | grep jwt`; if it shows '3.0.0.beta1', you are vulnerable.Check Version:
gem list | grep jwtVerify Fix Applied:
After update, run `gem list | grep jwt` and confirm version is not '3.0.0.beta1' (e.g., '3.0.0.beta2' or '2.7.1').📡 Detection & Monitoring
Log Indicators:
- Failed JWT validations with weak key errors
- Unusual authentication patterns or token reuse
Network Indicators:
- Increased requests to authentication endpoints with malformed tokens
SIEM Query:
source="application.log" AND "JWT" AND ("invalid" OR "weak key")