Ory Oathkeeper has a path traversal authorization bypass

Description

Ory Oathkeeper is vulnerable to an authorization bypass via HTTP path traversal. An attacker can craft a URL containing path traversal sequences (e.g. /public/../admin/secrets) that resolves to a protected path after normalization, but is matched against a permissive rule because the raw, un-normalized path is used during rule evaluation.

Preconditions

Ory Oathkeeper rules are typically configured with patterns like:

/public/<.*>   → allow unauthenticated access
/admin/<.*>    → require authentication

Without path normalization, a request to /public/../admin/secrets is matched against the raw path /public/../admin/secrets. This matches the /public/<.*> rule, bypassing the authentication required for /admin/secrets. After Ory Oathkeeper permits the request, the upstream server normalizes the path and serves the protected /admin/secrets resource.

Mitigation

Going forward, Ory Oathkeeper normalizes the request path before performing rule matching and before forwarding. The path /public/../admin/secrets is normalized to /admin/secrets, which correctly matches the /admin/<.*> rule and triggers authentication.

As an immediate mitigation, all requests reaching Oathkeeper should be normalized, as described in the section below. Oathkeeper should be upgraded to a fixed version as soon as possible.

Defense in depth: Cleaning paths before Oathkeeper

Even after this fix, it is good practice to normalize HTTP paths in the layers in front of Oathkeeper. This provides defense in depth and protects against similar bypasses in other components. The following examples show how to achieve this with common reverse proxies and CDNs.

Nginx

Nginx normalizes paths by default when using proxy_pass. Alternatively, use $uri (which Nginx normalizes) rather than $request_uri in your matching rules.

Envoy

Enable the normalize_path option (available since Envoy 1.14) to normalize the path components before matching and forwarding. See the <a href="https://www.envoyproxy.io/docs/envoy/latest/api-v3/extensions/filters/network/http_connection_manager/v3/http_connection_manager.proto#envoy-v3-api-field-extensions-filters-network-http-connection-manager-v3-httpconnectionmanager-normalize-path" target="_blank" rel="noopener noreferrer">Envoy docs on path normalization</a>.

Cloudflare

Cloudflare normalizes URLs by default. In the Cloudflare dashboard, ensure Normalize incoming URLs is enabled under Rules → Normalization. See the <a href="https://developers.cloudflare.com/rules/normalization/" target="_blank" rel="noopener noreferrer">Cloudflare URL normalization docs</a>.