CVE-2026-3125
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
Summary
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.
Affected Software
| Vendor | Product | Version Range | Status |
|---|---|---|---|
| opennextjs | @opennextjs/cloudflare | 0 < 1.17.1 | affected |
Weaknesses
- CWE-918: CWE-918 Server-Side Request Forgery (SSRF)
- CWE-706: CWE-706 Use of Incorrectly-Resolved Name or Reference
ADP Enrichment
CISA ADP Vulnrichment
- SSVC:
- Exploitation: none
- Automatable: yes
- Technical Impact: partial
References
- https://github.com/opennextjs/opennextjs-cloudflare/pull/1147
- https://www.npmjs.com/package/@opennextjs/cloudflare/v/1.17.1
- https://github.com/advisories/GHSA-rvpw-p7vw-wj3m
- https://www.cve.org/cverecord?id=CVE-2025-6087
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