CVE-2025-54888
📋 TL;DR
This CVE describes an authentication bypass vulnerability in Fedify, a TypeScript library for ActivityPub federated servers. It allows unauthenticated attackers to impersonate any ActivityPub actor by sending forged activities signed with their own keys, as verification occurs after processing. All Fedify instances using vulnerable versions are affected.
💻 Affected Systems
- Fedify
⚠️ Risk & Real-World Impact
Worst Case
Complete compromise of federated identity system allowing attackers to impersonate any user, post malicious content, manipulate social graphs, and potentially spread misinformation or malware across the entire ActivityPub network.
Likely Case
Attackers impersonate high-profile accounts to post spam, phishing links, or misinformation, damaging reputation and trust in affected platforms.
If Mitigated
With proper monitoring and quick response, impact is limited to temporary account misuse that can be rolled back, though trust may still be damaged.
🎯 Exploit Status
The vulnerability is straightforward to exploit as it involves sending forged activities without authentication.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 1.3.20, 1.4.13, 1.5.5, 1.6.8, 1.7.9, 1.8.5
Vendor Advisory: https://github.com/fedify-dev/fedify/security/advisories/GHSA-6jcc-xgcr-q3h4
Restart Required: Yes
Instructions:
1. Identify your Fedify version. 2. Update to the appropriate patched version using npm: npm update @fedify/fedify. 3. Restart your application server. 4. Verify the update was successful.
🔧 Temporary Workarounds
Temporary Activity Verification
allImplement custom middleware to verify actor signatures before processing activities.
🧯 If You Can't Patch
- Implement strict network-level controls to limit incoming ActivityPub traffic to trusted sources only.
- Deploy additional monitoring and alerting for suspicious activity patterns and actor impersonation attempts.
🔍 How to Verify
Check if Vulnerable:
Check package.json for Fedify version and compare against affected version ranges.Check Version:
npm list @fedify/fedifyVerify Fix Applied:
Verify the Fedify version is updated to one of the patched versions and test authentication flow with signed activities.📡 Detection & Monitoring
Log Indicators:
- Unusual activity from accounts, mismatched actor signatures in authentication logs, failed signature verification attempts
Network Indicators:
- Spike in ActivityPub traffic from unknown sources, unusual federation patterns
SIEM Query:
source="fedify" AND (event="authentication_failure" OR event="actor_impersonation")