VulnerabilityAnalyzed

CVE-2026-27191

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.

HIGH 7.4EPSS 0.25%

Does this matter?

High impact if exploited, but EPSS currently rates exploitation as unlikely (0.25%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.

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.

CVSS 4.0: 7.4 HIGHCVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:A/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/M
EPSS: 0.25% probability · 17th percentile
CISA KEV: Not listed
Weakness: CWE-601
Affected: feathersjs/feathers
Source: security-advisories@github.com

References

https://github.com/feathersjs/feathers/commit/ee19a0ae9bc2ebf23b1fe598a1f7361981b65401Patch
https://github.com/feathersjs/feathers/releases/tag/v5.0.40Product, Release Notes
https://github.com/feathersjs/feathers/security/advisories/GHSA-ppf9-4ffw-hh4pThird Party Advisory

Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.