Cloudanix VulnDB

GHSA-pxq7-h93f-9jrg

High · 8.2

OAuth2 Proxy has an Authentication Bypass via Fragment Confusion in skip_auth_routes and skip_auth_regex

CVSS

8.2

EPSS

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Published

Apr 15, 2026

CISA due date

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The record

A configuration-dependent authentication bypass exists in OAuth2 Proxy. Deployments are affected when all of the following are true: * Use of `skip_auth_routes` or the legacy `skip_auth_regex` * Use of patterns that can be widened by attacker-controlled suffixes, such as `^/foo/.*/bar$` causing potential exposure of `/foo/secret` * Protected upstream applications that interpret `#` as a fragment delimiter or otherwise route the request to the protected base path In deployments that rely on these settings, an unauthenticated attacker can send a crafted request containing a number sign in the path, including the browser-safe encoded form `%23`, so that OAuth2 Proxy matches a public allowlist rule while the backend serves a protected resource. Deployments that do not use these skip-auth options, or that only allow exact public paths with tightly scoped method and path rules, **ARE NOT** affected.

Affected packages

Ecosystem Package Introduced Fixed

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