CVE-2026-34240 in appsup-dart jose

Summary

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.

Responsible

GitHub_M

Reservation

03/26/2026

Disclosure

03/31/2026

Entries

VulDB provides additional information and datapoints for this CVE:

ID	Vulnerability	CWE	Exp	Cou	CVE
354436	appsup-dart jose JWS/JWT signature verification	347	Not defined	Official fix	CVE-2026-34240