Vulnerability · Published Mar 31, 2026 · Assigned by GitHub_M
CVE-2026-34240jose vulnerable to untrusted JWK header key acceptance during signature verification
High 7.5
In plain English
A high-severity security flaw in jose from appsup-dart. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.1% (higher than 3% of all known vulnerabilities).
Official description
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.
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| appsup-dart | jose | < 0.3.5+1 |
Weakness: CWE-347 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N