CVE-2026-3125SSRF vulnerability in opennextjs-cloudflare via /cdn-cgi/ path normalization bypass
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.
Data: CVE.org, NVD, CISA KEV, FIRST EPSS, Ubuntu. Published as the sources state it, in English.
Affected products and versions
| Vendor | Product | Versions | |
|---|---|---|---|
| opennextjs | opennext for cloudflare | < 1.17.1 | |
| opennextjs | @opennextjs/cloudflare | < 1.17.1 |
References and patches
- https://github.com/opennextjs/opennextjs-cloudflare/pull/1147 patchIssue TrackingPatch
- https://www.npmjs.com/package/@opennextjs/cloudflare/v/1.17.1 productProductRelease Notes
- https://github.com/advisories/GHSA-rvpw-p7vw-wj3m Third Party Advisory
- https://www.cve.org/cverecord?id=CVE-2025-6087 Third Party Advisory
CPE matches (NVD) (1)
cpe:2.3:a:opennextjs:opennext_for_cloudflare:*:*:*:*:*:node.js:*:*< 1.17.1