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Vulnerabilities

Vulnerability · CVE-2026-44351

fast-jwt provides fast JSON Web Token (JWT) implementation.

Published May 13, 2026 · catalog updated Jun 17, 2026 · fast-jwt provides fast JSON

Check if you run it

No confirmed exploitation is on record for CVE-2026-44351. EPSS is 0.33%. Act only if a listed version of fast-jwt provides fast JSON is installed.

Gaps on this record

  • The stored product name is a package slug. The name on this page is taken from the title (fast-jwt provides fast JSON).
  • No version range is stored. A customer cannot check an installed version against this record.
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
Severity
Critical9.1
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.33%
Remediation
Advisory link
Affected products
See sources for product scope

fast-jwt provides fast JSON Web Token (JWT) implementation. Prior to 6.2.4, a critical authentication-bypass vulnerability in fast-jwt's async key-resolver flow allows any unauthenticated attacker to forge arbitrary JWTs that are accepted as authentic. When the application's key resolver returns an empty string (''), for example via the common keys[decoded.header.kid] || '' JWKS-style fallback, fast-jwt converts it to a zero-length Buffer, hands it to crypto.createSecretKey, derives allowedAlgorithms = ['HS256','HS384','HS512'] from it, and then verifies the token's signature against an empty-key HMAC. The attacker simply computes HMAC-SHA256(key='', input='${header}.${payload}'), which Node accepts without complaint — and the verifier returns the attacker-chosen payload (sub, admin, scopes, etc.) as authentic. This vulnerability is fixed in 6.2.4.

No affected version ranges are stored yet. Use the vendor advisory before you decide this record does not apply.

How to fix CVE-2026-44351

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-2026-44351. EPSS is 0.33%. Act only if a listed version of fast-jwt provides fast JSON is installed.

Which versions are affected?

Affected version ranges are not on this record. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-1391; CWE-287: Improper Authentication; CWE-326: Inadequate Encryption Strength. EPSS 0.33%. 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. May 13, 2026 · NIST NVD

    Detected

    fast-jwt provides fast JSON Web Token (JWT) implementation. Prior to 6.2.4, a critical authentication-bypass vulnerability in fast-jwt's async key-resolver flow allows any unauthenticated attacker to forge arbitrary JWTs that are accepted as authentic. When the application's key resolver returns an empty string (''), for example via the common keys[decoded.header.kid] || '' JWKS-style fallback, fa

  2. Jun 17, 2026 · NIST NVD

    Updated

    fast-jwt provides fast JSON Web Token (JWT) implementation. Prior to 6.2.4, a critical authentication-bypass vulnerability in fast-jwt's async key-resolver flow allows any unauthenticated attacker to forge arbitrary JWTs that are accepted as authentic. When the application's key resolver returns an empty string (''), for example via the common keys[decoded.header.kid] || '' JWKS-style fallback, fa

Sources

  • CVE.orgVulnerability recordCVE-2026-44351

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2026-44351

    30-day exploitation probability 0.3%

    first.org
  • NIST NVDVulnerability recordCVE-2026-44351

    fast-jwt provides fast JSON Web Token (JWT) implementation. Prior to 6.2.4, a critical authentication-bypass vulnerability in fast-jwt's async key-resolver flow allows any unauthenticated attacker to forge arbitrary JWTs that are accepted as authentic. When the application's key

    nvd.nist.gov

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.