CRE-2025-0051

NGINX No Live Upstreams AvailableHigh

Impact: 9/10

Mitigation: 5/10

CRE-2025-0051View on GitHub

NginxLoad BalancerUpstream FailureConnectivity

Description

NGINX is reporting that all backend servers in an upstream group are unavailable. This means that NGINX cannot route requests to any of its configured backend servers, resulting in client-facing errors.

Mitigation

- Check the health and status of each backend server in the upstream group - Verify network connectivity between NGINX and the backend servers - Review the NGINX upstream configuration for errors or typos - Consider adding more backup servers to improve resilience - Implement automatic health checks and failover mechanisms - Ensure proper monitoring is in place to detect backend server failures quickly

References

• https://last9.io/blog/quick-fixes-for-upstream-connect-errors/
• https://nginx.org/en/docs/http/ngx_http_upstream_module.html