high · 7.5 Patched

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

CVE-2026-100409 · GHSA-2vc4-c4r6-p6v6 · published 15 Oct 2026

How serious is it

  • Severity: high, CVSS score 7.5 out of 10.
  • No exploit prediction (EPSS) score yet.
  • Not on the CISA list of exploited vulnerabilities.
  • No public exploit in Exploit-DB.

Is your app affected by CVE-2026-100409?

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Who is affected

  • @opennextjs/cloudflare (npm) >= 0.3.0, < 1.20.2

How to check

  1. Run npm ls @opennextjs/cloudflare in your project to see the installed version, including copies pulled in by other packages.
  2. Or paste your lockfile into the checker: it lists every package with a known vulnerability, this one included.
  3. Or run npx shippable-dev scan localhost:3000 in your project folder. It reads your lockfile and flags this vulnerability along with every other known one.

How to fix

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  1. Upgrade @opennextjs/cloudflare to 1.20.2 or later, commit the lockfile and redeploy.
  2. If a vulnerable version was live, check your logs and rotate the secrets that server could read.

The advisory

## 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.

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References

Merged from GitHub Advisory Database. Last updated 23 Oct 2026. All vulnerabilities · RSS · JSON