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
- Run
npm ls @opennextjs/cloudflarein your project to see the installed version, including copies pulled in by other packages. - Or paste your lockfile into the checker: it lists every package with a known vulnerability, this one included.
- Or run
npx shippable-dev scan localhost:3000in your project folder. It reads your lockfile and flags this vulnerability along with every other known one.
How to fix
Copies a prompt for Claude Code, Cursor or Codex: it checks your lockfiles for this and upgrades it.
- Upgrade
@opennextjs/cloudflareto 1.20.2 or later, commit the lockfile and redeploy. - 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.
Check your whole app
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References
- github.com/opennextjs/opennextjs-cloudflare/security/advisories/GHSA-2vc4-c4r6-p6v6
- nvd.nist.gov/vuln/detail/CVE-2026-100409
- github.com/opennextjs/opennextjs-aws/pull/1199
- github.com/opennextjs/opennextjs-aws/pull/1200
- github.com/opennextjs/opennextjs-cloudflare/commit/38ea40b669be272ddf09a7df7e70c69d0b57404b
- github.com/opennextjs/opennextjs-cloudflare/releases/tag/@opennextjs/cloudflare@1.20.2
- github.com/advisories/GHSA-2vc4-c4r6-p6v6
Merged from GitHub Advisory Database. Last updated 23 Oct 2026. All vulnerabilities · RSS · JSON