CVE-2026-42274: Github.com/dadrus/heimdall Heimdall Has An Authorization Bypass Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-3q34-rx83-r6mq",
  "modified" : "2026-05-12T13:29:02Z",
  "published" : "2026-04-25T23:30:46Z",
  "aliases" : [ "CVE-2026-42274" ],
  "summary" : "Heimdall has an authorization bypass via path normalization mismatch",
  "details" : "### Summary\n\nHeimdall 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`).\n\n### Details\n\nThis 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.\n\n```yaml\nid: rule-1\nmatch:\n  routes:\n    - path: /user/**\nexecute: # configured to require authentication and authorization\n  # ...\n```\n\n```yaml\nid: rule-2\nmatch:\n  routes:\n    - path: /public/**\nexecute: # configured to allow anonymous access\n  # ...\n```\n\nIf 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`.\n\n### Impact\n\nBypass of access control policies enforced by heimdall may lead to the following consequences:\n\n* Access to or modification of data that should be restricted\n* Invocation of functionality that is expected to require authentication or authorization\n* In certain configurations, escalation of privileges depending on the exposed functionality\n\n### Workarounds\n\n* 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)).\n* 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.",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:H/SI:H/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/dadrus/heimdall"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "0.17.14"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/dadrus/heimdall/security/advisories/GHSA-3q34-rx83-r6mq"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-42274"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/dadrus/heimdall/pull/3209"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/dadrus/heimdall/commit/b5dfa484b7a8c2ce6d8691c026f9da867719947a"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/dadrus/heimdall"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/dadrus/heimdall/releases/tag/v0.17.14"
  }, {
    "type" : "WEB",
    "url" : "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"
  }, {
    "type" : "WEB",
    "url" : "https://www.rfc-editor.org/rfc/rfc3986#section-6.2.2.3"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-35", "CWE-436" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-04-25T23:30:46Z",
    "nvd_published_at" : "2026-05-08T04:16:22Z"
  }
}