CVE-2023-31999
📋 TL;DR
CVE-2023-31999 is a CSRF vulnerability in @fastify/oauth2 where a static state parameter was reused across all users and requests, allowing attackers to bypass OAuth2 CSRF protection. This affects all applications using vulnerable versions of @fastify/oauth2 for OAuth2 authentication. Attackers could potentially hijack user authentication flows.
💻 Affected Systems
- @fastify/oauth2
📦 What is this software?
Oauth2 by Fastify
⚠️ Risk & Real-World Impact
Worst Case
Attackers could hijack OAuth2 authentication flows to gain unauthorized access to user accounts, potentially leading to account takeover and data compromise.
Likely Case
Attackers could perform CSRF attacks against OAuth2 flows, potentially redirecting users to malicious sites or intercepting authentication tokens.
If Mitigated
With proper state parameter validation, OAuth2 flows remain secure against CSRF attacks as intended.
🎯 Exploit Status
Exploitation requires the attacker to trick a user into initiating an OAuth2 flow, but the vulnerability makes CSRF protection ineffective.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: v7.2.0
Vendor Advisory: https://github.com/fastify/fastify-oauth2/releases/tag/v7.2.0
Restart Required: Yes
Instructions:
1. Update @fastify/oauth2 to version 7.2.0 or later using npm update @fastify/oauth2. 2. Review breaking changes in checkStateFunction. 3. Restart your application.
🔧 Temporary Workarounds
Implement custom state generation
allImplement a custom checkStateFunction that generates unique state parameters per user session
🧯 If You Can't Patch
- Implement additional CSRF protection mechanisms at the application level
- Monitor OAuth2 authentication logs for suspicious patterns
🔍 How to Verify
Check if Vulnerable:
Check package.json for @fastify/oauth2 version. If version is below 7.2.0, you are vulnerable.Check Version:
npm list @fastify/oauth2Verify Fix Applied:
Verify @fastify/oauth2 version is 7.2.0 or higher and test OAuth2 flows with unique state parameters.📡 Detection & Monitoring
Log Indicators:
- Multiple OAuth2 requests with identical state parameters
- OAuth2 callback requests with mismatched state parameters
Network Indicators:
- OAuth2 authorization requests with predictable state parameters
SIEM Query:
source="oauth2" AND state="static_value" OR state_reuse=true🔗 References
- https://auth0.com/docs/secure/attack-protection/state-parameters
- https://github.com/fastify/fastify-oauth2/releases/tag/v7.2.0
- https://hackerone.com/reports/2020418
- https://auth0.com/docs/secure/attack-protection/state-parameters
- https://github.com/fastify/fastify-oauth2/releases/tag/v7.2.0
- https://hackerone.com/reports/2020418
