CVE-2026-34083 signalk-server: OAuth Authorization Code Theft via Unvalidated Host Header in OIDC Flow
Attackers can steal OAuth authorization codes by spoofing the Host header, leading to session hijacking in Signal K Server deployments.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2026-34083?
CVE-2026-34083 is a medium-severity vulnerability in signalk-server, published on 2 Apr 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official description
Signal K Server is a server application that runs on a central hub in a boat. Prior to version 2.24.0, SignalK Server contains a code-level vulnerability in its OIDC login and logout handlers where the unvalidated HTTP Host header is used to construct the OAuth2 redirect_uri. Because the redirectUri configuration is silently unset by default, an attacker can spoof the Host header to steal OAuth authorization codes and hijack user sessions in realistic deployments as The OIDC provider will then send the authorization code to whatever domain was injected. This issue has been patched in version 2.24.0.
Which versions are affected by CVE-2026-34083?
2 open source packages ship an affected version, including signalk-server. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
signalk-server npm | From 2.20.0 | 2.24.0 |
signalk-server npm | From 2.20.0 | 2.24.0 |
Products include Signalk Signal K Server.
How do I fix CVE-2026-34083?
Upgrade signalk-server to 2.24.0 or later.
Is CVE-2026-34083 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-34083 exists.
Other vulnerabilities in signalk-server
- CVE-2026-23515 RCE - Command Injection in Signal K set-system-time plugin
- CVE-2025-66398 Signal K Server has Unauthenticated State Pollution leading to Remote Code Execution (RCE)
- CVE-2026-33950 signalk-server: Privilege Escalation by Admin Role Injection via /enableSecurity
- CVE-2025-68620 Signal K Server vulnerable to JWT Token Theft via WebSocket Enumeration and Unauthenticated Polling
- CVE-2026-41893 Signal K Server's WebSocket Login Endpoint Lacks Rate Limiting (Credential Brute-Force)
Sources
Also known as GHSA-cxj8-ggf2-p57c.