OpenNext Cloudflare: Cache interception can bypass middleware protection for encoded paths

## Summary When cache interception is enabled, `@opennextjs/cloudflare` can interpret percent-encoded paths differently during middleware matching and cache lookup. An 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. `enableCacheInterception` is disabled by default. ## Impact A remote unauthenticated attacker may retrieve cached content from routes intended to be protected by middleware. An application is affected when it: - explicitly enables `enableCacheInterception`; - relies on middleware for access control; and - has a matching cached route. ## Details Middleware matching previously used the encoded request pathname, while cache interception decoded the pathname before selecting a cache entry. For example, consider an application with: - middleware matcher `/admin/:path*`; - middleware returning `401 Authentication required` for `/admin`; - a statically generated, cached `/admin` route; and - cache interception enabled: ```ts export default defineCloudflareConfig({ incrementalCache: staticAssetsIncrementalCache, enableCacheInterception: true, }); ``` An attacker can request: ```http GET /%61dmin ``` The 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: ```http HTTP/1.1 200 OK x-opennext-cache: HIT Protected content ``` Malformed paths exposed an additional inconsistency. For example: ```http GET /%61dmin/%ZZ ``` The 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. ## Patches The 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). Users should upgrade to `@opennextjs/cloudflare@1.20.2` or later. ## Workarounds If upgrading is not immediately possible for an application: 1. Disable cache interception by removing `enableCacheInterception: true`. 2. Enforce authorization inside protected route handlers rather than relying exclusively on middleware. 3. Reject encoded paths for protected routes at a trusted proxy before they reach the Worker. Adding individual encoded matcher variants is not a complete workaround because pathnames can have multiple equivalent encodings. Source Code Location: https://github.com/opennextjs/opennextjs-cloudflare Affected Packages: - npm:@opennextjs/cloudflare, affected >= 0.3.0, < 1.20.2, patched in 1.20.2 CWEs: - CWE-177: Improper Handling of URL Encoding (Hex Encoding) - CWE-180: Incorrect Behavior Order: Validate Before Canonicalize CVSS: - Primary: score 7.5, CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N - CVSS_V3: score 7.5, CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N References: - https://github.com/opennextjs/opennextjs-cloudflare/security/advisories/GHSA-2vc4-c4r6-p6v6 - https://nvd.nist.gov/vuln/detail/CVE-2026-100409 - https://github.com/opennextjs/opennextjs-aws/pull/1199 - https://github.com/opennextjs/opennextjs-aws/pull/1200 - https://github.com/opennextjs/opennextjs-cloudflare/commit/38ea40b669be272ddf09a7df7e70c69d0b57404b - https://github.com/opennextjs/opennextjs-cloudflare/releases/tag/@opennextjs/cloudflare@1.20.2 - https://github.com/advisories/GHSA-2vc4-c4r6-p6v6