CVE-2024-8796
📋 TL;DR
Devise-Two-Factor versions 2.2.0 through 5.x generate TOTP shared secrets with insufficient entropy (120 bits instead of required 128 bits), making two-factor authentication codes easier to brute-force. This affects Ruby on Rails applications using devise-two-factor gem for multi-factor authentication. Attackers could potentially bypass 2FA protection.
💻 Affected Systems
- devise-two-factor Ruby gem
📦 What is this software?
Devise Two Factor by Tinfoilsecurity
Devise Two Factor by Tinfoilsecurity
⚠️ Risk & Real-World Impact
Worst Case
Complete 2FA bypass allowing unauthorized account access to sensitive systems or data.
Likely Case
Increased risk of successful brute-force attacks against 2FA-protected accounts, particularly for high-value targets.
If Mitigated
Minimal impact if proper rate limiting, monitoring, and strong passwords are in place alongside 2FA.
🎯 Exploit Status
Exploitation requires ability to capture or predict TOTP codes and brute-force the shorter secret space.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 6.0.0
Vendor Advisory: https://github.com/devise-two-factor/devise-two-factor/security/advisories/GHSA-qjxf-mc72-wjr2
Restart Required: Yes
Instructions:
1. Update Gemfile to 'gem "devise-two-factor", ">= 6.0.0"'. 2. Run 'bundle update devise-two-factor'. 3. Restart application server. 4. Existing users must re-enroll their 2FA devices as secrets will be regenerated.
🔧 Temporary Workarounds
Manual secret regeneration
allForce regeneration of all TOTP secrets with proper 128-bit length
# In Rails console: User.find_each { |u| u.otp_secret = User.generate_otp_secret; u.save }
🧯 If You Can't Patch
- Implement strict rate limiting on authentication attempts
- Monitor for unusual authentication patterns and failed 2FA attempts
🔍 How to Verify
Check if Vulnerable:
Check Gemfile.lock for devise-two-factor version between 2.2.0 and 5.xCheck Version:
bundle show devise-two-factorVerify Fix Applied:
Verify Gemfile.lock shows devise-two-factor version 6.0.0 or higher📡 Detection & Monitoring
Log Indicators:
- Multiple failed 2FA attempts from same IP/user
- Successful authentication after many 2FA failures
Network Indicators:
- Unusual authentication request patterns to 2FA endpoints
SIEM Query:
source="application.log" ("failed 2fa" OR "invalid totp") count by user_ip > threshold