CVE-2026-34240

JOSE is a Javascript Object Signing and Encryption (JOSE) library. Prior to version 0.3.5+1, a vulnerability in jose could allow an unauthenticated, remote attacker to forge valid JWS/JWT tokens by using a key embedded in the JOSE header (jwk). The vulnerability exists because key selection could treat header-provided jwk as a verification candidate even when that key was not present in the trusted key store. Since JOSE headers are untrusted input, an attacker could exploit this by creating a token payload, embedding an attacker-controlled public key in the header, and signing with the matching private key. Applications using affected versions for token verification are impacted. This issue has been patched in version 0.3.5+1. A workaround for this issue involves rejecting tokens where header jwk is present unless that jwk matches a key already present in the application's trusted key store.

The following products are affected by CVE-2026-34240 vulnerability.

Here, you will find a curated list of external links that provide in-depth information to CVE-2026-34240.

URL	Resource
https://github.com/appsup-dart/jose/commit/b07799aac1f56a9a21483feac026272aab30cc5d
https://github.com/appsup-dart/jose/security/advisories/GHSA-vm9r-h74p-hg97