CVE-2026-34083
MEDIUMCVE-2026-34083 is a medium-severity (CVSS 6.1) CWE-346 vulnerability in signalk-server. O3 Security confirms whether CVE-2026-34083 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
signalk-server: OAuth Authorization Code Theft via Unvalidated Host Header in OIDC Flow
Real-World Exposure
How broadly this vulnerability is actually deployed: weekly install volume shows current usage, a proxy for how much of the ecosystem is exposed.
signalk-servernpmDescription
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.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | signalk-server | ≥ 2.20.0&&< 2.24.0 | 2.24.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for signalk-server. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update signalk-server to 2.24.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-34083 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2026-34083 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2026-34083. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-34083 in your dependencies?
O3 detects CVE-2026-34083 across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.