CVE-2026-26205: Github.com/open policy agent/opa envoy plugin Opa-envoy-plugin Has An Authorization Bypass Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-9f29-v6mm-pw6w",
  "modified" : "2026-02-19T21:56:34Z",
  "published" : "2026-02-18T15:25:04Z",
  "aliases" : [ "CVE-2026-26205" ],
  "summary" : "opa-envoy-plugin has an Authorization Bypass via Double-Slash Path Misinterpretation in input.parsed_path",
  "details" : "A security vulnerability has been discovered in how the `input.parsed_path` field is constructed. HTTP request paths are treated as full URIs when parsed; interpreting leading path segments prefixed with double slashes (`//`) as [authority](https://datatracker.ietf.org/doc/html/rfc3986#section-3.2) components, and therefore dropping them from the parsed path. This creates a path interpretation mismatch between authorization policies and backend servers, enabling attackers to bypass access controls by crafting requests where the authorization filter evaluates a different path than the one ultimately served.\n\n#### Attack example\n\n**HTTP request:**\n\n```\nGET //admin/users HTTP/1.1\nHost: example.com\n```\n\n**Policy sees:**\n\nThe leading `//admin` path segment is interpreted as an authority component, and dropped from `input.parsed_path` field:\n\n\n```json\n{\n  \"parsed_path\": [\"users\"]\n}\n```\n\n**Backend receives:**\n\n`//admin/users` path, normalized to `/admin/users`.\n\n#### Affected Request Pattern Examples\n\n| Request path | `input.parsed_path` | `input.attributes.request.http.path` | Discrepancy |\n| - | - | - | - |\n| / | [\"\"] | / | ✅ None |\n| //foo  | [\"\"] | //foo| ❌ Mismatch |\n| /admin | [\"admin\"] | /admin | ✅ None |\n| /admin/users | [\"admin\", \"users\"] |  /admin/users | ✅ None |\n| //admin/users  | [\"users\"] | //admin/users | ❌ Mismatch |\n\n### Impact\n\nUsers are impacted if all the following conditions apply:\n\n1. Protected resources are path-hierarchical (e.g., `/admin/users` vs `/users`)\n2. Authorization policies use `input.parsed_path` for path-based decisions\n3. Backend servers apply lenient path normalization\n\n### Patches\n\nGo: `v1.13.2-envoy-2`\nDocker: `1.13.2-envoy-2`, `1.13.2-envoy-2-static`\n\n### Workarounds\n\nUsers who cannot immediately upgrade opa-envoy-plugin are recommended to apply one, or more, of the workarrounds described below.\n\n#### 1. Enable the `merge_slashes` Envoy configuration option\n\nAs per [Envoy best practices](https://www.envoyproxy.io/docs/envoy/v1.37.0/configuration/best_practices/edge.html), enabling the [merge_slashes](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-merge-slashes) configuration option in Envoy will remove redundant slashes from the request path before filtering is applied, effectively mitigating the `input.parsed_path` issue described in this advisory.\n\n\n#### 2. Use `input.attributes.request.http.path` instead of `input.parsed_path` in policies\n\nThe `input.attributes.request.http.path` field contains the unprocessed, raw request path. Users are recommended to update any policy using `input.parsed_path` to instead use the `input.attributes.request.http.path` field.\n\n##### Example ####\n\n```rego\npackage example\n\n# Use instead of input.parsed_path\nparsed_path := split(                                        # tokenize into array\n\ttrim_left(                                               # drop leading slashes\n\t\turlquery.decode(input.attributes.request.http.path), # url-decode the path\n\t\t\"/\",\n\t),\n\t\"/\",\n)\n```",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:N/SC:H/SI:H/SA:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/open-policy-agent/opa-envoy-plugin"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "1.13.2-envoy-2"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 1.13.1-envoy"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/open-policy-agent/opa-envoy-plugin/security/advisories/GHSA-9f29-v6mm-pw6w"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-26205"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/open-policy-agent/opa-envoy-plugin/commit/58c44d4ec408d5852d1d0287599e7d5c5e2bc5c3"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/open-policy-agent/opa-envoy-plugin"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/open-policy-agent/opa-envoy-plugin/releases/tag/v1.13.2-envoy-2"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-863" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-02-18T15:25:04Z",
    "nvd_published_at" : "2026-02-19T20:25:43Z"
  }
}