GitHub Advisoryadvisory · Pub
GHSA-vm9r-h74p-hg97 jose vulnerable to untrusted JWK header key acceptance during signature verification
HIGH
Official page ↗
- Aliases
- CVE-2026-34240
- Ecosystem
- Pub
- Packages
- jose
- Severity
- High
- CVSS vector
- CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
- Weaknesses
- CWE-347
- Reviewed
- 2026-03-31
Affected packages
• Pub jose: < 0.3.5+1 → fixed in 0.3.5+1
Description
Impact
A vulnerability in `jose` versions up to and including `0.3.5` 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.
Patches
Upgrade to `0.3.5+1` or later.
Workarounds
Reject tokens where header `jwk` is present unless that `jwk` matches a key already present in the application's trusted key store.
Resources
Fix commit: fix: improved key resolution in JsonWebKeyStore
Related
Alias · CVE (1)
- CVE-2026-34240 JOSE is a Javascript Object Signing and Encryption (JOSE) library. vulnerability
Weakness · CWE (1)
- CWE-347 Improper Verification of Cryptographic Signature weakness