CVE-2025-27421
📋 TL;DR
A critical goroutine leak vulnerability in Abacus server's Server-Sent Events implementation allows resource exhaustion when clients disconnect from the /stream endpoint. This affects all Abacus deployments using SSE functionality, causing the server to eventually stop accepting new connections while maintaining high memory usage.
💻 Affected Systems
- Abacus
⚠️ 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
Complete denial of service where the Abacus server becomes unresponsive to new SSE connections, requiring server restart and potentially causing service disruption.
Likely Case
Gradual performance degradation leading to eventual service unavailability for SSE endpoints, requiring manual intervention to restart the service.
If Mitigated
Minimal impact with proper monitoring and automated restart mechanisms in place to detect and recover from resource exhaustion.
🎯 Exploit Status
Exploitation requires only normal client disconnection behavior, making it trivial to trigger.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 1.4.0
Vendor Advisory: https://github.com/JasonLovesDoggo/abacus/security/advisories/GHSA-vh64-54px-qgf8
Restart Required: Yes
Instructions:
1. Stop the Abacus service. 2. Update to version 1.4.0 or later. 3. Restart the Abacus service.
🔧 Temporary Workarounds
Disable SSE endpoint
allTemporarily disable the /stream endpoint if SSE functionality is not required
Modify configuration to disable SSE or block access to /stream endpoint
Implement connection limits
linuxUse reverse proxy or load balancer to limit concurrent connections to /stream endpoint
Configure nginx/haproxy with connection limits for /stream path
🧯 If You Can't Patch
- Implement aggressive monitoring for goroutine count and memory usage with automated alerts
- Schedule regular service restarts to clear accumulated goroutines before resource exhaustion occurs
🔍 How to Verify
Check if Vulnerable:
Check if Abacus version is below 1.4.0 and /stream endpoint is enabledCheck Version:
Check application logs or run 'abacus --version' if availableVerify Fix Applied:
Confirm version is 1.4.0 or later and monitor goroutine count during client disconnections📡 Detection & Monitoring
Log Indicators:
- Increasing goroutine count in metrics
- Memory usage growth without corresponding traffic increase
- Failed SSE connection attempts
Network Indicators:
- Increased connection attempts to /stream endpoint
- SSE connections remaining open abnormally long
SIEM Query:
source="abacus" ("goroutine" OR "memory") count>threshold