CVE-2026-27193 Feathers exposes internal headers via unencrypted session cookie
Attackers can decode session cookies to expose internal headers, API keys, and infrastructure details when deployed behind proxies.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-27193?
CVE-2026-27193 is a high-severity vulnerability in feathersjs feathers, published on 21 Feb 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Feathersjs is a framework for creating web APIs and real-time applications with TypeScript or JavaScript. In versions 5.0.39 and below, all HTTP request headers are stored in the session cookie, which is signed but not encrypted, exposing internal proxy/gateway headers to clients. The OAuth service stores the complete headers object in the session, then the session is persisted using cookie-session, which base64-encodes the data. While the cookie is signed to prevent tampering, the contents are readable by anyone by simply decoding the base64 value. Under specific deployment configurations (e.g., behind reverse proxies or API gateways), this can lead to exposure of sensitive internal infrastructure details such as API keys, service tokens, and internal IP addresses. This issue has been fixed in version 5.0.40.
Weakness: CWE-200
Which versions are affected by CVE-2026-27193?
2 open source packages ship an affected version, including @feathersjs/authentication-oauth. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
@feathersjs/authentication-oauth npm | All versions | 5.0.40 |
@feathersjs/authentication-oauth npm | All versions | 5.0.40 |
Products include Feathersjs Feathers.
How do I fix CVE-2026-27193?
Upgrade @feathersjs/authentication-oauth to 5.0.40 or later.
Is CVE-2026-27193 being exploited?
There is no known exploitation of CVE-2026-27193 in the wild and no public exploit code.
Other vulnerabilities in feathersjs feathers
- CVE-2026-29792 Feathersjs has an OAuth Callback Account Takeover
- CVE-2026-29793 NoSQL Injection via WebSocket id Parameter in MongoDB Adapter
- CVE-2026-27192 Feathers has an origin validation bypass via prefix matching
- CVE-2023-37899 feathersjs socket handler allows abusing implicit toString
- CVE-2026-27191 Feathers: Open Redirect in OAuth callback enables account takeover
Sources
Also known as GHSA-9m9c-vpv5-9g85.