The vulnerability in the Echo framework allows a remote client to supply an X‑Real‑IP header that is forwarded unchanged to upstream services when the IPExtractor is not configured. This flaw, mapped to CWE‑346 (Broken Access Control), lets an attacker masquerade as any client IP address, thereby bypassing IP‑based access controls, rate limiting, audit logging, and geographic restrictions that rely on the forwarded identity. The impact is a loss of confidentiality and integrity of access controls, as well as potential availability issues if upstream resources are exposed to unintended traffic.

Labstack Echo web framework versions 4.0.0 through 5.4.0 are affected. The issue is resolved in Echo 5.4.0 and later releases. System administrators should identify any installations of Echo within that version range that allow unconfigured IP extraction.

The CVSS base score for this issue is 5.3, indicating moderate severity. EPSS data is not available, and the vulnerability is not listed in CISA’s KEV catalog. The attack vector is remote: an attacker sends an HTTP request containing a forged X‑Real‑IP header to the Echo application. No local privilege or authentication is required, so the threat is purely external and relies on the application trusting the header value.