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High

Feathers has an origin validation bypass via prefix matching

Type: advisorySources: OSV

Feathersjs is a framework for creating web APIs and real-time applications with TypeScript or JavaScript. In versions 5.0.39 and below, origin validation uses startsWith() for comparison, allowing attackers to bypass the check by registering a domain that shares a common prefix with an allowed origin.The getAllowedOrigin() function checks if the Referer header starts with any allowed origin, and this comparison is insufficient as it only validates the prefix. This is exploitable when the origins array is configured and an attacker registers a domain starting with an allowed origin string (e.g., https://target.com.attacker.com bypasses https://target.com). On its own, tokens are still redirected to a configured origin. However, in specific scenarios an attacker can initiate the OAuth flow from an unauthorized origin and exfiltrate tokens, achieving full account takeover. This issue has bee fixed in version 5.0.40.

Products
Not specified
Affected versions
Not specified
Fixed versions
Not specified
CVEs
CVE-2026-27192
Confirmed fixed CVEs
Not specified
Updated in this feed
7 Nov 2026, 03:43 UTC · Revision 1

Source evidence

Feathers has an origin validation bypass via prefix matching

core-osv · Original source

Published 21 Feb 2026, 03:50 UTC

Feathersjs is a framework for creating web APIs and real-time applications with TypeScript or JavaScript. In versions 5.0.39 and below, origin validation uses startsWith() for comparison, allowing attackers to bypass the check by registering a domain that shares a common prefix with an allowed origin.The getAllowedOrigin() function checks if the Referer header starts with any allowed origin, and this comparison is insufficient as it only validates the prefix. This is exploitable when the origins array is configured and an attacker registers a domain starting with an allowed origin string (e.g., https://target.com.attacker.com bypasses https://target.com). On its own, tokens are still redirected to a configured origin. However, in specific scenarios an attacker can initiate the OAuth flow from an unauthorized origin and exfiltrate tokens, achieving full account takeover. This issue has bee fixed in version 5.0.40.

osv:CVE-2026-27192
Complete source record
{
  "id": "78e8263ce8414abc407b178c78021c69fc9c790d7ffacb50b53944a71cbe9a0a",
  "url": "https://osv.dev/vulnerability/CVE-2026-27192",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Feathers has an origin validation bypass via prefix matching",
    "summary": "Feathersjs is a framework for creating web APIs and real-time applications with TypeScript or JavaScript. In versions 5.0.39 and below, origin validation uses startsWith() for comparison, allowing attackers to bypass the check by registering a domain that shares a common prefix with an allowed origin.The getAllowedOrigin() function checks if the Referer header starts with any allowed origin, and this comparison is insufficient as it only validates the prefix. This is exploitable when the origins array is configured and an attacker registers a domain starting with an allowed origin string (e.g., https://target.com.attacker.com bypasses https://target.com). On its own, tokens are still redirected to a configured origin. However, in specific scenarios an attacker can initiate the OAuth flow from an unauthorized origin and exfiltrate tokens, achieving full account takeover. This issue has bee fixed in version 5.0.40.",
    "evidence": "osv:CVE-2026-27192",
    "products": [],
    "severity": "high",
    "structured": {
      "id": "CVE-2026-27192",
      "aliases": [
        "CVE-2026-27192",
        "GHSA-mp4x-c34x-wv3x"
      ],
      "metrics": [
        {
          "type": "CVSS_V4",
          "score": "CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:P/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/feathersjs/feathers",
              "type": "GIT",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "f71178917bf5d38f2591c412b0f6edc69f211ee8"
                },
                {
                  "fixed": "ee19a0ae9bc2ebf23b1fe598a1f7361981b65401"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "cpe": "cpe:2.3:a:feathersjs:feathers:*:*:*:*:*:node.js:*:*",
                    "range": [
                      {
                        "introduced": "0"
                      },
                      {
                        "fixed": "5.0.40"
                      }
                    ],
                    "source": "CPE_RANGE"
                  },
                  {
                    "range": [
                      {
                        "fixed": "ee19a0ae9bc2ebf23b1fe598a1f7361981b65401"
                      }
                    ],
                    "source": "REFERENCES_COMMIT"
                  },
                  {
                    "range": [
                      {
                        "fixed": "f71178917bf5d38f2591c412b0f6edc69f211ee8"
                      }
                    ],
                    "source": "REFERENCES_TAG",
                    "original_tag": "v5.0.40"
                  }
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          "database_specific": {
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        }
      ],
      "modified": "2026-10-28T02:30:49.767627058Z",
      "provider": "osv",
      "references": [
        "https://github.com/feathersjs/feathers/releases/tag/v5.0.40",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/27xxx/CVE-2026-27192.json",
        "https://github.com/feathersjs/feathers/security/advisories/GHSA-mp4x-c34x-wv3x",
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        "value": "CVE-2026-27192",
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    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 517851,
  "published_at": "2026-02-21T03:50:35.954+00:00"
}