GHSA-vm9r-h74p-hg97 · Severity: high · Ecosystem: pub — jose vulnerable to untrusted JWK header key acceptance during signature verification
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.
Conclusion & alert: CVE-2026-34240 is rated Low Risk (30.6/100): CVSS High severity, with low exploitation likelihood (EPSS 0.01%). Mandatory action: Monitor for updates and reassess as exploit intelligence or EPSS changes.
Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.
EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).
| # | Date | Old EPSS score | New EPSS score | Delta (New - Old) |
|---|---|---|---|---|
| 1 | 2026-04-01 | — | 0.01% | — |
Full EPSS history (1 record total)
CVSS metrics for this CVE.
| Base score | Version | Severity | Vector | Exploitability | Impact | Score source |
|---|---|---|---|---|---|---|
| 7.5 | 3.1 | HIGH |
|
3.9 | 3.6 | [email protected] |
GHSA-vm9r-h74p-hg97 · Severity: high · Ecosystem: pub — jose vulnerable to untrusted JWK header key acceptance during signature verification
| Vendor | Product | Version | Raw CPE |
|---|---|---|---|
| appsup-dart | jose | < 0.3.5\+1 | cpe:2.3:a:appsup-dart:jose:*:*:*:*:*:*:*:* |