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Vulnerabilities

Vulnerability · CVE-2026-34240

JOSE is a Javascript Object Signing and Encryption (JOSE) library.

Published Mar 31, 2026 · catalog updated Jul 24, 2026 · JOSE is a Javascript

Check if you run it

No confirmed exploitation is on record for CVE-2026-34240. EPSS is 0.19%. Act only if a listed version of JOSE is a Javascript is installed.

Gaps on this record

  • The stored product name is a package slug. The name on this page is taken from the title (JOSE is a Javascript).
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
Severity
High7.5
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.19%
Remediation
Advisory link
Affected products
Pub jose · cpe appsup-dart/jose

### Impact A vulnerability in versions up to and including could allow an unauthenticated, remote attacker to forge valid JWS/JWT tokens by using a key embedded in the JOSE header ( ). The vulnerability exists because key selection could treat header-provided 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 or later. ### Workarounds Reject tokens where header is present unless that matches a key already present in the application's trusted key store. ### Resources Fix commit: [fix: improved key resolution in JsonWebKeyStore](https://github.com/appsup-dart/jose/commit/b07799aac1f56a9a21483feac026272aab30cc5d)

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • Pub jose0 → 0.3.5+1
  • cpe appsup-dart/joseversion unspecified

How to fix CVE-2026-34240

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2026-34240. EPSS is 0.19%. Act only if a listed version of JOSE is a Javascript is installed.

Which versions are affected?

Compare what you have installed with 0 → 0.3.5+1. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-347: Improper Verification of Cryptographic Signature. EPSS 0.19%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

Timeline

Detection, updates, and resolution for this record.

  1. Mar 31, 2026 · NIST NVD

    Detected

    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 truste

  2. Mar 31, 2026 · GitHub Advisory Database

    Fix available

    jose fixed in 0.3.5+1

  3. Jul 24, 2026 · GitHub Advisory Database

    Fix available

    jose fixed in 0.3.5+1

  4. Jul 24, 2026 · NIST NVD

    Updated

    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 truste

Sources

  • CVE.orgVulnerability recordCVE-2026-34240

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2026-34240

    30-day exploitation probability 0.2%

    first.org
  • GitHub Advisory DatabasePackage advisoryGHSA-vm9r-h74p-hg97

    GitHub Advisory Database record mirrored by OSV.

    github.com
  • NIST NVDVulnerability recordCVE-2026-34240

    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 ke

    nvd.nist.gov
  • OpenSSF OSV / OSV ScannerPackage advisoryGHSA-vm9r-h74p-hg97

    jose vulnerable to untrusted JWK header key acceptance during signature verification

    osv.dev

References

Freshness

Last verified in this catalog Oct 18, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.