# CVE-2026-100409: OpenNext Cloudflare: Cache interception can bypass middleware protection for encoded paths

> Attackers can bypass middleware authorization by using encoded paths to access cached protected content in OpenNext Cloudflare applications.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 15 Oct 2026
- **Updated:** 15 Oct 2026
- **Also known as:** GHSA-2vc4-c4r6-p6v6

## What is CVE-2026-100409?

CVE-2026-100409 is a high-severity authentication bypass vulnerability in opennextjs-cloudflare, published on 15 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

OpenNext Cloudflare is an open Next.js adapter for Cloudflare. From 0.3.0 until 1.20.2, applications that enable enableCacheInterception, rely on middleware for access control, and have a matching cached protected route process encoded pathnames inconsistently between middleware matching and cache lookup. An unauthenticated attacker can use a percent-encoded pathname that does not match authorization middleware but decodes to the cache key of a protected route, causing cached content to be returned without authorization. Malformed encodings can also be partially decoded, allowing cache lookup to continue with a pathname that middleware did not evaluate consistently. This issue is fixed in version 1.20.2.

Weakness: CWE-180 (Incorrect Behavior Order: Validate Before Canonicalize), CWE-177 (Improper Handling of URL Encoding (Hex Encoding))

## Which versions are affected by CVE-2026-100409?

2 open source packages ship an affected version, including @opennextjs/cloudflare.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `@opennextjs/cloudflare` | npm | From 0.3.0 | 1.20.2 |
| `@opennextjs/cloudflare` | npm | From 0.3.0 | 1.20.2 |

## How do I fix CVE-2026-100409?

Upgrade @opennextjs/cloudflare to 1.20.2 or later.

## Is CVE-2026-100409 being exploited?

There is no known exploitation of CVE-2026-100409 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-100409 and fix it if it is affected.

What it is: CVE-2026-100409 is a high-severity authentication bypass vulnerability in opennextjs-cloudflare, published on 15 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-100409 in the wild and no public exploit code.

Affected packages and fixed versions:
- @opennextjs/cloudflare (npm): affected from 0.3.0; fixed in 1.20.2
- @opennextjs/cloudflare (npm): affected from 0.3.0; fixed in 1.20.2

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-100409/ (Markdown: https://insights.sbomify.com/CVE-2026-100409/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-100409
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-100409
- OSV: https://osv.dev/vulnerability/CVE-2026-100409

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-100409/
Summaries are generated and may contain mistakes; the official description above is the record.