{"id":"CVE-2026-34240","aliases":["GHSA-vm9r-h74p-hg97"],"url":"https://o3.security/vulnerability/CVE-2026-34240","summary":"jose vulnerable to untrusted JWK header key acceptance during signature verification","details":"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.","published":"2026-03-31T15:44:23.578Z","modified":"2026-08-12T03:51:48.483745449Z","cvss":{"score":7.5,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N"},"epss":null,"cisaKev":null,"exploitsKnown":null,"affectedPackages":[{"ecosystem":"Pub","name":"jose","fixedVersion":"0.3.5+1"}],"fix":{"url":"https://github.com/appsup-dart/jose/commit/b07799aac1f56a9a21483feac026272aab30cc5d","label":"appsup-dart/jose@b07799a"},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/34xxx/CVE-2026-34240.json"},{"type":"ADVISORY","url":"https://github.com/appsup-dart/jose/security/advisories/GHSA-vm9r-h74p-hg97"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-34240"},{"type":"FIX","url":"https://github.com/appsup-dart/jose/commit/b07799aac1f56a9a21483feac026272aab30cc5d"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T03:51:48.483745449Z"}}