CVE-2026-107720

Status: DeferredHigh (7.4)—

fast-jwt provides fast JSON Web Token (JWT) implementation. Prior to 6.3.1, fast-jwt createVerifier accepts an unsigned JWT when key is an empty string or null and algorithms is a non-empty allowlist. Falsy synchronous keys bypass prepareKeyOrSecret, allowedAlgorithms remains active, hasKey is false, and the empty signature avoids the verifySignature gate. An attacker can therefore submit a token containing arbitrary claims without possessing a signing key, resulting in authentication or authorization bypass. Claim validators still run, and non-empty keys, an empty key without algorithms, and the async key resolver path do not have this behavior. This issue is fixed in version 6.3.1.

CVSS

Version: 3.1
Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
Base score: 7.4

Exploitation probability (EPSS)

Probability of exploitation in the next 30 days: 0.26%
Percentile among all scored CVEs: 16
Score date: 10/15/2026

EPSS (Exploit Prediction Scoring System, FIRST) estimates how likely a vulnerability is to be exploited in the wild within 30 days. It complements CVSS (impact) and CISA KEV (confirmed exploitation).

🎯 ATT&CK techniques

How this vulnerability is exploited and what the attacker gains, in MITRE ATT&CK terms.

ExploitationT1190 Exploit Public-Facing Applicationinitial access85 %
Primary impactT1078 Valid Accountsstealth · persistence · privilege escalation · initial access90 %
Secondary impactT1556 Modify Authentication Processdefense impairment · persistence · credential access75 %

Aplicación expuesta en red (AV:N) permite bypass de verificación JWT con clave vacía, resultando en autenticación/autorización falsa sin posesión de clave de firma (CWE-347).

Inferred by our analysis agent from the official description, CVSS vector and CWE, and checked by a supervisor. May contain errors.

🛡️ ATT&CK mitigations that cover these techniques

Privileged Account Management User Account Management Password Policies Multi-factor Authentication Application Developer Guidance Active Directory Configuration

Affected technologies (1)

⚠ AI-inferred from the description — NVD hasn't analyzed this CVE yet, these aren't verified CPEs.

Nearform — Fast-jwt^AI

CWEs

CWE-20, CWE-347

References

Raw JSON (NVD)

Show

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