Summary
Feathers exposes internal headers via unencrypted session cookie
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:
// https://github.com/feathersjs/feathers/blob/dove/packages/authentication-oauth/src/service.ts#L173
session.headers = headers;
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.
Credits: Abdelwahed Madani Yousfi (@vvxhid) / Edoardo Geraci (@b0-n0-b0) / Thomas Rinsma (@ThomasRinsma) From Codean Labs.
Impact
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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Frequently Asked Questions
- What is CVE-2026-27193? CVE-2026-27193 is a high-severity security vulnerability in @feathersjs/authentication-oauth (npm), affecting versions <= 5.0.39. It is fixed in 5.0.40.
- Which versions of @feathersjs/authentication-oauth are affected by CVE-2026-27193? @feathersjs/authentication-oauth (npm) versions <= 5.0.39 is affected.
- Is there a fix for CVE-2026-27193? Yes. CVE-2026-27193 is fixed in 5.0.40. Upgrade to this version or later.
- Is CVE-2026-27193 exploitable, and should I be worried? Whether CVE-2026-27193 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-27193 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-27193? Upgrade
@feathersjs/authentication-oauthto 5.0.40 or later.