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High, CVSS 7.6amended

Feathers has an origin validation bypass via prefix matching

CVE-2026-27192GHSA-mp4x-c34x-wv3x

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (@feathersjs/authentication-oauth 5.0.40), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS 4.0
7.6 · 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 · score source
EPSS
  • CVE-2026-27192: 0.27% estimated exploitation activity in the next 30 days; percentile 19.31 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

The 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: 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. Credits: Abdelwahed Madani Yousfi (@vvxhid) / Edoardo Geraci (@b0-n0-b0) / Thomas Rinsma (@ThomasRinsma) From Codean Labs.

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 3 · amended ·

    Amended from ghsa record GHSA-mp4x-c34x-wv3x

  2. Revision 2 · amended ·

    Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

  3. Revision 1 · created ·

    Published from osv record GHSA-mp4x-c34x-wv3x

Agent brief

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: CVE-2026-27192

Advisory: Feathers has an origin validation bypass via prefix matching
IDs: CVE-2026-27192, GHSA-mp4x-c34x-wv3x
Record: https://patchnext.com/advisories/cve-2026-27192 (revision 3, source checked 26 Oct 2026, 12:42 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.6)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: @feathersjs/authentication-oauth 5.0.40. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm @feathersjs/authentication-oauth: affected <= 5.0.39; fixed in 5.0.40

## Suggested inspection (read-only)
- `npm ls @feathersjs/authentication-oauth --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on @feathersjs/authentication-oauth.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-mp4x-c34x-wv3x (OSV record GHSA-mp4x-c34x-wv3x lists affected ranges: npm @feathersjs/authentication-oauth >=0 <5.0.40 (fixed))
- Verified: https://github.com/advisories/GHSA-mp4x-c34x-wv3x (GitHub-reviewed advisory GHSA-mp4x-c34x-wv3x lists affected ranges: npm @feathersjs/authentication-oauth >=0 <=5.0.39)

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