Skip to content
Heist/ feed
High

fast-jwt : Silent claim-validator bypass when JWT payload is a JSON array

Type: advisorySource: Official CVE List1 source record

fast-jwt provides fast JSON Web Token (JWT) implementation. Prior to 6.3.0, fast-jwt createVerifier accepts a validly signed JWT whose payload is a JSON array because src/decoder.js checks that the payload is an object but does not reject arrays. The claim validator loop then finds no named exp, nbf, iss, aud, sub, jti, or nonce properties and silently skips those configured checks, returning the array as a successfully verified payload. An attacker who can produce or influence a validly signed token may bypass expiry, issuer, audience, subject, revocation, and replay protections. The opt-in requiredClaims option can block missing claims, and signature verification itself is not bypassed. This issue is fixed in version 6.3.0.

Announced Source revision 1
Original source ↗

CVE-2026-107723

Primary source · Revision 1

Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.

Security context

Source reference: cve:CVE-2026-107723

fast-jwt

Source reference: /containers/cna/affected/0/product

Affected versions
Not stated in this record
Fixed versions
Not stated in this record
Prerequisites
Not stated in this record

Structured affected-version data

Original package identities and version rules from this source.

[
  {
    "vendor": "nearform",
    "product": "fast-jwt",
    "versions": [
      {
        "status": "affected",
        "version": "< 6.3.0"
      }
    ]
  }
]
Related CVEs
CVE-2026-107723

Source reference: /cveMetadata/cveId

Publisher severity

high

Source reference: /containers/cna/metrics

Event
#21336 · Revision 1
Added to Heist Feed
Publisher date
Read the original announcement