{"id":"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.","aliases":["GHSA-vm9r-h74p-hg97"],"modified":"2026-04-02T13:29:22.475073Z","published":"2026-03-31T15:44:23.578Z","database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/34xxx/CVE-2026-34240.json","cwe_ids":["CWE-347"],"cna_assigner":"GitHub_M"},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/34xxx/CVE-2026-34240.json"},{"type":"FIX","url":"https://github.com/appsup-dart/jose/commit/b07799aac1f56a9a21483feac026272aab30cc5d"},{"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"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/appsup-dart/jose","events":[{"introduced":"0"},{"last_affected":"5a8511ab1f71b7a892a930b35a402d3b19d96f72"}],"database_specific":{"versions":[{"introduced":"0"},{"last_affected":"\u003c 0.3.5+1"}]}}],"versions":["jose-v0.3.3","jose-v0.3.5","jose-v0.3.5+1"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-34240.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N"}]}