Vulnerability 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.
CVSS Score
HIGH
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Appsup-Dart | Jose | < 0.3.5\+1 |
Related Weaknesses (CWE)
References
- https://github.com/appsup-dart/jose/commit/b07799aac1f56a9a21483feac026272aab30cPatch
- https://github.com/appsup-dart/jose/security/advisories/GHSA-vm9r-h74p-hg97Vendor Advisory
FAQ
What is CVE-2026-34240?
CVE-2026-34240 is a vulnerability with a CVSS score of 7.5 (HIGH). 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 us...
How severe is CVE-2026-34240?
CVE-2026-34240 has been rated HIGH with a CVSS base score of 7.5/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-34240?
Check the references section above for vendor advisories and patch information. Affected products include: Appsup-Dart Jose.