{"id":"CVE-2026-26205","aliases":["GHSA-9f29-v6mm-pw6w","GO-2026-4506"],"url":"https://o3.security/vulnerability/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```","published":"2026-02-19T19:31:26.905Z","modified":"2026-08-12T03:51:48.185584021Z","cvss":null,"epss":null,"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"Go","name":"github.com/open-policy-agent/opa-envoy-plugin","fixedVersion":"1.13.2-envoy-2"}],"fix":{"url":"https://github.com/open-policy-agent/opa-envoy-plugin/commit/58c44d4ec408d5852d1d0287599e7d5c5e2bc5c3","label":"open-policy-agent/opa-envoy-plugin@58c44d4"},"references":[{"type":"WEB","url":"https://github.com/open-policy-agent/opa-envoy-plugin/releases/tag/v1.13.2-envoy-2"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/26xxx/CVE-2026-26205.json"},{"type":"ADVISORY","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":"FIX","url":"https://github.com/open-policy-agent/opa-envoy-plugin/commit/58c44d4ec408d5852d1d0287599e7d5c5e2bc5c3"},{"type":"PACKAGE","url":"https://github.com/open-policy-agent/opa-envoy-plugin"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T03:51:48.185584021Z"}}