CVE-2026-62987: Fabio - Incomplete fix for CVE-2025-48865: operator-configured trust headers (clientip/tls/requestid) still strippable via the Connection header

Vulnerability summary

CVE-2026-62987 is a medium (CVSS 5.8) Authentication Bypass by Spoofing vulnerability in fabiolb fabio. EPSS estimates a 0.20% chance of exploitation in the next 30 days, higher than 10.2% of scored vulnerabilities.

Timeline

1. 21-09-2026
   PublishedVulnerability first disclosed.
2. 21-09-2026
   Last modifiedVulnerability information updated.

Description

Fabio is an HTTP(S) and TCP router for deploying applications managed by consul. From 1.6.6 until 1.7.2, the CVE-2025-48865 fix in proxy/http_headers.go uses protectHeaders for a hardcoded set of forwarded headers but omits the operator-configured ClientIPHeader, TLSHeader, and RequestID names. In proxy/http_proxy.go, HTTPProxy.ServeHTTP calls addHeaders to set these trust headers before Go ReverseProxy processes the inbound Connection header, allowing an unauthenticated client to name and remove the configured headers before the request reaches the backend. Deployments that enable the corresponding proxy.header options can therefore lose client-IP, TLS-termination, or request-correlation signals used by backend authorization and auditing; the options are empty by default, and the hardcoded protected forwarded headers are unaffected. This issue is fixed in version 1.7.2.

• CWE-290Authentication Bypass by SpoofingThis attack-focused weakness is caused by incorrectly implemented authentication schemes that are subject to spoofing attacks.
• CWE-348Use of Less Trusted SourceThe product has two different sources of the same data or information, but it uses the source that has less support for verification, is less trusted, or is less resistant to attack.