Signal K Server builds the OAuth2 redirect_uri using the supplied HTTP Host header without validation during OIDC login and logout. This flaw allows an attacker to craft a surrogate Host value that tricks the OpenID Connect provider into sending the authorization code to an attacker‑controlled domain, giving the attacker tokens and enabling session hijacking. The weakness is reflected in CWE‑346 and CWE‑601.

All installations of Signal K Server running a version earlier than 2.24.0 are affected. The vulnerability is present in the OIDC login and logout handlers and impacts any maritime vessel or central hub that has not applied the 2.24.0 release.

The CVSS rating of 6.1 denotes medium severity, and the EPSS score of less than 1 % indicates a low probability of exploitation in the immediate future. The vulnerability is not listed in CISA’s KEV catalog. An attacker who can send HTTP requests to the server can manipulate the Host header remotely, making the attack vector network‑based. Successful exploitation permits an attacker to obtain OAuth authorization codes and hijack user sessions without needing to compromise user credentials.