GitHub Advisoryadvisory · Pub

GHSA-vm9r-h74p-hg97 jose vulnerable to untrusted JWK header key acceptance during signature verification

HIGH Published 2026-03-31 Modified 2026-03-31 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

References