CVE-2026-62987: Fabio - Incomplete fix for CVE-2025-48865: operator-configured trust headers (clientip/tls/requestid) still strippable via the Connection header
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/httpheaders.go uses protectHeaders for a hardcoded set of forwarded headers but omits the operator-configured ClientIPHeader, TLSHeader, and RequestID names. In proxy/httpproxy.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.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
fabioto a version that resolves this vulnerability.Fixed in 1.7.2
Event History
Frequently Asked Questions
Which deployments are affected in practice?
Affected deployments run Fabio from 1.6.6 until 1.7.2 and have configured one or more corresponding proxy.header options for ClientIPHeader, TLSHeader, or RequestID. These options are empty by default, so deployments that have not enabled them are not exposed through this issue.
What does an attacker need to do to exploit this?
An unauthenticated client only needs network access to send an HTTP request through the Fabio proxy. The client can use the inbound Connection header to name configured trust headers and cause them to be removed before the request reaches the backend.
What is the impact on backend applications?
Backends can lose client-IP, TLS-termination, or request-correlation signals when they rely on the configured trust headers. This can affect authorization decisions and auditing that depend on those signals, while the hardcoded protected forwarded headers remain unaffected.
What can be done if upgrading is not immediately possible?
Disable the corresponding configured proxy.header options for client IP, TLS, and request ID where operationally feasible. This removes the affected operator-configured trust-header names; the options are empty by default.
How can I determine whether my deployment is affected?
Check whether Fabio is in the 1.6.6 through 1.7.2 range and inspect its configuration for non-empty proxy.header settings corresponding to ClientIPHeader, TLSHeader, or RequestID. Fabio 1.7.2 contains the fix.