Jose EUVD-2026-17498

Remote unauthenticated attacker exploiting JOSE library versions prior to 0.3.5+1 when application accepts jwk header parameter for key selection without validating against trusted keystore. No user interaction required.

This vulnerability presents HIGH real-world risk despite moderate CVSS 7.5 scoring. The CVSS vector (AV:N/AC:L/PR:N/UI:N) confirms network-exploitable attacks with low complexity requiring no authentication or user interaction, though impact is limited to integrity (I:H) rather than confidentiality or availability. The exploitation scenario is straightforward: attackers generate their own RSA/EC key pair, embed the public key in the 'jwk' header, sign malicious claims (e.g., admin privileges, altered user IDs), and the vulnerable library accepts it as valid. No specialized tools are required beyond standard JWT libraries. The authentication bypass impact is severe for applications using this library for access control, session management, or API authorization. While no CISA KEV listing or public exploit code exists, the technical barrier is extremely low-any developer familiar with JWT structure can exploit this. The GitHub commit fix (b07799aac1f56a9a21483feac026272aab30cc5d) confirms vendor acknowledgment and remediation, reducing ongoing risk for patched systems.

An attacker targeting a Dart-based API uses a JWT manipulation tool to craft a malicious access token. They generate a fresh RSA-2048 key pair, create a JWT payload claiming admin privileges (e.g., {"sub":"attacker","role":"admin"}), embed their public key in the JOSE header as {"alg":"RS256","jwk":{"kty":"RSA","n":"[modulus]","e":"AQAB"}}, and sign with their private key. When submitted to the vulnerable API endpoint, the jose library extracts the attacker's public key from the header and successfully validates the self-signed token, granting unauthorized administrative access. The attack requires no prior authentication, leaves minimal forensic traces in standard logs, and can be automated against multiple applications using the vulnerable library version.