CVE-2026-3125

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.

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.

A Server-Side Request Forgery (SSRF) vulnerability was identified in the @opennextjs/cloudflare package. The vulnerability stems from an unimplemented feature in the Cloudflare adapter for Open Next, which allowed unauthenticated users to proxy arbitrary remote content via the `/_next/image` endpoint. This issue allowed attackers to load remote resources from arbitrary hosts under the victim site’s domain for any site deployed using the Cloudflare adapter for Open Next. For example: `https://victim-site.com/_next/image?url=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. ### Impact - SSRF via unrestricted remote URL loading - Arbitrary remote content loading - Potential internal service exposure or phishing risks through domain abuse ### Mitigation The following mitigations have been put in place: **Server side updates** to Cloudflare’s platform to restrict the content loaded via the `/_next/image` endpoint to images. The update automatically mitigates the issue for all existing and any future sites deployed to Cloudflare using the affected version of the Cloudflare adapter for Open Next **Root cause fix**: Pull request https://github.com/opennextjs/opennextjs-cloudflare/pull/727 to the Cloudflare adapter for Open Next. The patched version of the adapter is found here [@opennextjs/cloudflare@1.3.0](https://www.npmjs.com/package/@opennextjs/cloudflare/v/1.3.0) **Package dependency update**: Pull request https://github.com/cloudflare/workers-sdk/pull/9608 to create-cloudflare (c3) to use the fixed version of the Cloudflare adapter for Open Next. The patched version of create-cloudflare is found at [create-cloudflare@2.49.3](https://www.npmjs.com/package/create-cloudflare/v/2.49.3). In addition to the automatic mitigation deployed on Cloudflare’s platform, we encourage affected users to upgrade to @opennext/cloudflare v1.3.0 and use the [remotePatterns](https://nextjs.org/docs/pages/api-reference/components/image#remotepatterns) filter in Next config if they need to allow-list external urls with images assets. ### Credits Disclosed responsibly by security researcher Edward Coristine. Thank you for the report. ### References https://www.cve.org/cverecord?id=CVE-2025-6087

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. ### Impact - SSRF via path normalization bypass of Cloudflare edge interception - Arbitrary remote content loading under the victim site's domain - Same-origin policy bypass - Potential for infrastructure abuse (scanning from Cloudflare IP space, worker resource exhaustion) - Exposure of private assets stored under /cdn-cgi/ paths. For example, Open Next projects store incremental cache data under /cdn-cgi/_next_cache, which could be exposed via this bypass. ### Credits Disclosed responsibly by security researcher @Ezzer17. ### Mitigations The following mitigations have been put in place: Server-side updates to Cloudflare's Workers platform to block backslash path normalization bypasses for /cdn-cgi requests. The update automatically mitigates the issue for all existing and any future sites deployed to Cloudflare Workers. In addition to the platform level fix, [Root cause fix](https://github.com/opennextjs/opennextjs-cloudflare/pull/1147) has been implemented to the Cloudflare adapter for Open Next. The patched version of the adapter is found at @opennextjs/cloudflare@1.17.1 (https://www.npmjs.com/package/@opennextjs/cloudflare) [Dependency update](https://github.com/opennextjs/opennextjs-cloudflare/pull/1150) to the Next.js template used with create-cloudflare (c3) to use the fixed version of the Cloudflare adapter for Open Next. Despite the automatic mitigation deployed on Cloudflare's platform, we encourage affected users to upgrade to the patched version of @opennextjs/cloudflare.

Una vulnerabilidad de falsificación de petición del lado del servidor (SSRF) fue identificada en el paquete @opennextjs/cloudflare, resultante de un bypass de normalización de ruta en el gestor /cdn-cgi/image/. La plantilla de worker @opennextjs/cloudflare incluye un gestor /cdn-cgi/image/ destinado solo para uso en desarrollo. En producción, el edge de Cloudflare intercepta las peticiones /cdn-cgi/image/ antes de que lleguen al Worker. Sin embargo, al sustituir una barra invertida por una barra inclinada (/cdn-cgi\image/ en lugar de /cdn-cgi/image/), un atacante puede eludir la intercepción del edge y hacer que la petición llegue directamente al Worker. La clase URL de JavaScript luego normaliza la barra invertida a una barra inclinada, haciendo que la petición coincida con el gestor y desencadene una obtención no validada de URLs remotas arbitrarias. Por ejemplo: https://victim-site.com/cdn-cgi\image/aaaa/https://attacker.com En este ejemplo, contenido controlado por el atacante de attacker.com se sirve a través del dominio del sitio víctima (victim-site.com), violando la política de mismo origen y potencialmente engañando a usuarios u otros servicios. Nota: Este bypass solo funciona a través de clientes HTTP que preservan las barras invertidas en las rutas (p. ej., curl --path-as-is). Los navegadores normalizan las barras invertidas a barras inclinadas antes de enviar las peticiones. Además, Cloudflare Workers con Assets y Cloudflare Pages sufren de una vulnerabilidad similar. Los Assets almacenados bajo rutas /cdn-cgi/ no son accesibles públicamente bajo condiciones normales. Sin embargo, utilizando el mismo bypass de barra invertida (/cdn-cgi\... en lugar de /cdn-cgi/...), estos assets se vuelven accesibles públicamente. Esto podría usarse para recuperar datos privados. Por ejemplo, los proyectos Open Next almacenan datos de caché incremental bajo /cdn-cgi/_next_cache, que podrían ser expuestos a través de este bypass.