CVE-2026-40910: frp: Authentication bypass in frp HTTP vhost routing when routeByHTTPUser is used for access control

Severity: critical (CVSS 9.1 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2026-04-21 · updated 2026-10-26
Weakness: CWE-287

Description

frp is a fast reverse proxy. From 0.43.0 to 0.68.0, frp contains an authentication bypass in the HTTP vhost routing path when routeByHTTPUser is used as part of access control. In proxy-style requests, the routing logic uses the username from Proxy-Authorization to select the routeByHTTPUser backend, while the access control check uses credentials from the regular Authorization header. As a result, an attacker who can reach the HTTP vhost entrypoint and knows or can guess the protected routeByHTTPUser value may access a backend protected by httpUser / httpPassword even with an incorrect Proxy-Authorization password. This issue affects deployments that explicitly use routeByHTTPUser. It does not affect ordinary HTTP proxies that do not use this feature. This vulnerability is fixed in 0.68.1.

Affected products

fatedier frp: from 0.43.0 before 0.68.1 — fixed in 0.68.1

How to fix

Upgrade to a fixed version: fatedier frp 0.68.1. Check the vendor advisory for mitigations.

References

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