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

Quick assessment

Affected
opennextjs @opennextjs/cloudflare
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

OpenNext for Cloudflare是OpenNext开源的一个将Next.js应用部署到Cloudflare的适配器。 OpenNext for Cloudflare存在安全漏洞，该漏洞源于路径规范化绕过，可能导致服务端请求伪造和私有数据泄露。

AI Predicted 8.6 Difficulty: Easy EPSS 0.44% · P37
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I. Basic Information for CVE-2026-3125

Vulnerability Information
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Vulnerability Title
SSRF vulnerability in opennextjs-cloudflare via /cdn-cgi/ path normalization bypass
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
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
Source: CVE Program / CVE List V5
Vulnerability Type
服务端请求伪造(SSRF)
Source: CVE Program / CVE List V5
Vulnerability Title
OpenNext for Cloudflare 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
OpenNext for Cloudflare是OpenNext开源的一个将Next.js应用部署到Cloudflare的适配器。 OpenNext for Cloudflare存在安全漏洞，该漏洞源于路径规范化绕过，可能导致服务端请求伪造和私有数据泄露。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
opennextjs @opennextjs/cloudflare 0 ~ 1.17.1 -

II. Public POCs for CVE-2026-3125

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III. Intelligence Information for CVE-2026-3125

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Patches & Fixes for CVE-2026-3125 (1)

Vendor Advisories for CVE-2026-3125 (2)

IV. Related Vulnerabilities

Same vendor: opennextjs
Same weakness: CWE-918

V. Comments for CVE-2026-3125

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