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

Type: advisorySources: OSV

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/...),

Products
Not specified
Affected versions
Not specified
Fixed versions
Not specified
CVEs
CVE-2025-6087, CVE-2026-3125
Confirmed fixed CVEs
Not specified
Updated in this feed
3 Nov 2026, 16:54 UTC · Revision 1

Source evidence

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

core-osv · Original source

Published 4 Mar 2026, 18:14 UTC

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/...),

osv:CVE-2026-3125
Complete source record
{
  "id": "4ecd45542157d0d15aed0c6002733d5159454ae180342759f9b847f34e3096f0",
  "url": "https://osv.dev/vulnerability/CVE-2026-3125",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "SSRF vulnerability in opennextjs-cloudflare via /cdn-cgi/ path normalization bypass",
    "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/...),",
    "evidence": "osv:CVE-2026-3125",
    "products": [],
    "severity": "high",
    "structured": {
      "id": "CVE-2026-3125",
      "aliases": [
        "CVE-2025-6087",
        "CVE-2026-3125",
        "GHSA-c7mq-gh6q-6q7c",
        "GHSA-rvpw-p7vw-wj3m"
      ],
      "metrics": [
        {
          "type": "CVSS_V4",
          "score": "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"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/opennextjs/opennextjs-cloudflare",
              "type": "GIT",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "206794f1341023294147e7ef0b09146b7c7caaeb"
                }
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              "database_specific": {
                "extracted_events": [
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                        "introduced": "0"
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                      {
                        "fixed": "1.17.1"
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                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StandardRange"
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                  {
                    "cpe": "cpe:2.3:a:opennextjs:opennext_for_cloudflare:*:*:*:*:*:node.js:*:*",
                    "range": [
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            "@opennextjs/cloudflare@1.10.0",
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          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-3125.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:30.597508885Z",
      "provider": "osv",
      "references": [
        "https://www.cve.org/cverecord?id=CVE-2025-6087",
        "https://www.npmjs.com/package/@opennextjs/cloudflare",
        "https://www.npmjs.com/package/@opennextjs/cloudflare/v/1.17.1",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/3xxx/CVE-2026-3125.json",
        "https://github.com/advisories/GHSA-rvpw-p7vw-wj3m",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-3125",
        "https://github.com/opennextjs/opennextjs-cloudflare/pull/1147",
        "https://github.com/opennextjs/opennextjs-cloudflare"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-706",
          "CWE-918"
        ],
        "cna_assigner": "cloudflare",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/3xxx/CVE-2026-3125.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2025-6087",
        "evidence": "/aliases"
      },
      {
        "value": "CVE-2026-3125",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 497617,
  "published_at": "2026-03-04T18:14:31.111+00:00"
}