{"id":"CVE-2026-100409","aliases":["GHSA-2vc4-c4r6-p6v6"],"url":"https://o3.security/vulnerability/CVE-2026-100409","summary":"OpenNext Cloudflare: Cache interception can bypass middleware protection for encoded paths","details":"## Summary\n\nWhen cache interception is enabled, `@opennextjs/cloudflare` can interpret percent-encoded paths differently during middleware matching and cache lookup.\n\nAn encoded request may fail to match authorization middleware, then be decoded into the cache key of a protected route. The cached response may consequently be returned without invoking the middleware.\n\n`enableCacheInterception` is disabled by default.\n\n## Impact\n\nA remote unauthenticated attacker may retrieve cached content from routes intended to be protected by middleware.\n\nAn application is affected when it:\n\n- explicitly enables `enableCacheInterception`;\n- relies on middleware for access control; and\n- has a matching cached route.\n\n## Details\n\nMiddleware matching previously used the encoded request pathname, while cache interception decoded the pathname before selecting a cache entry.\n\nFor example, consider an application with:\n\n- middleware matcher `/admin/:path*`;\n- middleware returning `401 Authentication required` for `/admin`;\n- a statically generated, cached `/admin` route; and\n- cache interception enabled:\n\n```ts\nexport default defineCloudflareConfig({\n  incrementalCache: staticAssetsIncrementalCache,\n  enableCacheInterception: true,\n});\n```\n\nAn attacker can request:\n\n```http\nGET /%61dmin\n```\n\nThe encoded pathname does not match `/admin/:path*`, so the authorization middleware is not invoked. Cache interception then decodes `%61dmin` to `admin` and may return the cached `/admin` response:\n\n```http\nHTTP/1.1 200 OK\nx-opennext-cache: HIT\n\nProtected content\n```\n\nMalformed paths exposed an additional inconsistency. For example:\n\n```http\nGET /%61dmin/%ZZ\n```\n\nThe previous implementation decoded each segment independently. It decoded `%61dmin` to `admin` but retained the malformed `%ZZ` segment, allowing cache lookup to continue using a partially decoded pathname.\n\n## Patches\n\nThe fix aligns encoded-path handling across middleware matching and cache lookup, and rejects malformed paths instead of partially decoding them. See the upstream fixes in [opennextjs-aws#1199](https://github.com/opennextjs/opennextjs-aws/pull/1199) and [opennextjs-aws#1200](https://github.com/opennextjs/opennextjs-aws/pull/1200).\n\nUsers should upgrade to `@opennextjs/cloudflare@1.20.2` or later.\n\n## Workarounds\n\nIf upgrading is not immediately possible for an application:\n\n1. Disable cache interception by removing `enableCacheInterception: true`.\n2. Enforce authorization inside protected route handlers rather than relying exclusively on middleware.\n3. Reject encoded paths for protected routes at a trusted proxy before they reach the Worker.\n\nAdding individual encoded matcher variants is not a complete workaround because pathnames can have multiple equivalent encodings.","published":"2026-10-15T16:57:50.999Z","modified":"2026-10-24T02:30:27.617333035Z","cvss":{"score":7.5,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N"},"epss":null,"cisaKev":null,"exploitsKnown":null,"affectedPackages":[{"ecosystem":"npm","name":"@opennextjs/cloudflare","fixedVersion":"1.20.2"}],"fix":{"url":"https://github.com/opennextjs/opennextjs-aws/pull/1199","label":"opennextjs/opennextjs-aws#1199"},"references":[{"type":"WEB","url":"https://github.com/opennextjs/opennextjs-cloudflare/releases/tag/@opennextjs/cloudflare@1.20.2"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/100xxx/CVE-2026-100409.json"},{"type":"ADVISORY","url":"https://github.com/opennextjs/opennextjs-cloudflare/security/advisories/GHSA-2vc4-c4r6-p6v6"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-100409"},{"type":"FIX","url":"https://github.com/opennextjs/opennextjs-aws/pull/1199"},{"type":"FIX","url":"https://github.com/opennextjs/opennextjs-aws/pull/1200"},{"type":"FIX","url":"https://github.com/opennextjs/opennextjs-cloudflare/commit/38ea40b669be272ddf09a7df7e70c69d0b57404b"},{"type":"PACKAGE","url":"https://github.com/opennextjs/opennextjs-cloudflare"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-10-24T02:30:27.617333035Z"}}