Описание
OAuth2 Proxy has an Authentication Bypass via Fragment Confusion in skip_auth_routes and skip_auth_regex
Impact
A configuration-dependent authentication bypass exists in OAuth2 Proxy.
Deployments are affected when all of the following are true:
- Use of
skip_auth_routesor the legacyskip_auth_regex* Use of patterns that can be widened by attacker-controlled suffixes, such as^/foo/.*/bar$causing potential exposure of/foo/secret* Protected upstream applications that interpret#as a fragment delimiter or otherwise route the request to the protected base path
In deployments that rely on these settings, an unauthenticated attacker can send a crafted request containing a number sign in the path, including the browser-safe encoded form %23, so that OAuth2 Proxy matches a public allowlist rule while the backend serves a protected resource.
Deployments that do not use these skip-auth options, or that only allow exact public paths with tightly scoped method and path rules, ARE NOT affected.
Patches
A fix has been implemented to normalize request paths more conservatively before skip-auth matching so fragment content does not influence allowlist decisions.
Released as part of v7.15.2
Workarounds
Users who cannot upgrade immediately can reduce exposure by tightening or removing skip_auth_routes and skip_auth_regex rules, especially patterns that use broad wildcards across path segments.
Recommended mitigations:
- Replace broad rules with exact, anchored public paths and explicit HTTP methods
- Reject requests whose path contains
%23or#at the ingress, load balancer, or WAF level - Avoid placing sensitive application paths behind broad
skip_auth_routesrules
Пакеты
github.com/oauth2-proxy/oauth2-proxy/v7
>= 7.5.0, < 7.15.2
7.15.2
Связанные уязвимости
OAuth2 Proxy is a reverse proxy that provides authentication using OAuth2 providers. Versions 7.5.0 through 7.15.1 have a configuration-dependent authentication bypass. Deployments are affected when all of the following are true: Use of `skip_auth_routes` or the legacy `skip_auth_regex`; use of patterns that can be widened by attacker-controlled suffixes, such as `^/foo/.*/bar$` causing potential exposure of `/foo/secret`; and 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 affect...
OAuth2 Proxy is a reverse proxy that provides authentication using OAuth2 providers. Versions 7.5.0 through 7.15.1 have a configuration-dependent authentication bypass. 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`; and 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.
OAuth2 Proxy is a reverse proxy that provides authentication using OAu ...