CVE-2026-42274 — Vulnerability in github.com/dadrus/heimdall — CVE...

### Summary Heimdall performs rule matching on the raw (non-normalized) request path, while downstream components may normalize dot-segments according to [RFC 3986, Section 6.2.2.3](https://www.rfc-editor.org/rfc/rfc3986#section-6.2.2.3). This discrepancy can result in heimdall authorizing a request for one path (e.g., `/user/../admin`, or URL-encoded variants such as `/user/%2e%2e/admin` or `/user/%2e%2e%2fadmin`. The latter would require the `allow_encoded_slashes` option to be set to `on` or `no_decode`.) while the downstream ultimately processes a different, normalized path (`/admin`). ### Details This vulnerability can be exploited by an adversary if rule matching is performed using free (named or unnamed) wildcards without further constraints, as shown in the example snippets below. ```yaml id: rule-1 match: routes: - path: /user/** execute: # configured to require authentication and authorization # ... ``` ```yaml id: rule-2 match: routes: - path: /public/** execute: # configured to allow anonymous access # ... ``` If an adversary sends a request to `/public/../user/whatever`, rule-2 will be matched and executed. The downstream service may, however, normalize the request path and interpret it as `/user/whatever`. ### Impact Bypass of access control policies enforced by heimdall may lead to the following consequences: * Access to or modification of data that should be restricted * Invocation of functionality that is expected to require authentication or authorization * In certain configurations, escalation of privileges depending on the exposed functionality ### Workarounds * Normalize HTTP paths or reject HTTP paths containing relative path expressions in the layers in front of Heimdall - this is good practice anyway. Some proxies do that by default, such as Traefik; others, such as Envoy, require additional configuration (for Envoy see [`normalize_path`](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)). * Include the ID of the rule expected to be executed in the JWT issued by heimdall and check that value in the consuming project's service.