CVE-2026-34240
JOSE is a Javascript Object Signing and Encryption (JOSE) library.
Published Mar 31, 2026 · corrected/updated Jul 24, 2026 · appsup-dart jose · evidence confidence high
### 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)
Grounded briefings
Catalog interpretations for three audiences. Each brief cites ingested metadata and the original advisories below. They are not independent research and they do not invent exploit steps.
Executive
CVE-2026-34240 is a high public vulnerability record for appsup-dart jose. It is not currently listed in the CISA Known Exploited catalog. Check the linked vendor or CERT advisories for patch status. This summary is a catalog interpretation of the ingested metadata and cites the original advisories below.
System administrator
Identify whether appsup-dart jose is in your estate, then compare installed versions with the affected ranges. Affected packages or ranges on record: jose (0 → 0.3.5+1); appsup-dart/jose. Check the linked vendor or CERT advisories for patch status. Prefer the vendor or distribution advisory linked in Sources before changing production systems. This is a catalog interpretation, not a runbook.
Security analyst
Signals on file: CVSS 7.5. It is not currently listed in the CISA Known Exploited catalog. Weakness classes: CWE-347. Sources contributing to this record: cve_org, github, nvd, osv. Public exploit references, when present, are outbound links only and are not proof of active exploitation. This is a catalog interpretation of stored metadata.
Exploitation and remediation
Exploitation evidence
Not listed as known exploited in CISA KEV. Not in CISA KEV or VulnCheck KEV.
Patch and remediation
No required-action text is stored yet. Use the vendor or CERT links in Sources for patch availability.
Safe detection guidance
Compare installed versions with the affected ranges below and verify the advisory from the original publisher. This site stores metadata and outbound links only; it does not ship exploit code or proof-of-concept payloads.
Code
The project this record applies to. Exploit listings stay in References.
Timeline
Detection, updates, and resolution for this record.
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
Mar 31, 2026 · GitHub Advisory Database
Fix available
jose fixed in 0.3.5+1
Jul 24, 2026 · GitHub Advisory Database
Fix available
jose fixed in 0.3.5+1
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
Affected
- Pub jose0 → 0.3.5+1
- cpe appsup-dart/joseversion unspecified
Sources
- CVE.orgVulnerability recordCVE-2026-34240
Official CVE identifier
cve.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