CVE-2026-107721

Status: DeferredMedium (5.9)—

fast-jwt provides fast JSON Web Token (JWT) implementation. Prior to 6.3.0, fast-jwt createVerifier accepts Infinity for clockTolerance because its option validation checks type and negativity but not finiteness. In validateClaimDateValue, infinite positive and negative modifiers make exp and nbf comparisons always pass, allowing expired or not-yet-active tokens to be accepted. The verifier cache also derives infinite bounds, so entries created under this configuration can remain valid until eviction. Exploitation requires an application administrator or equivalent configuration path to set clockTolerance to Infinity. This issue is fixed in version 6.3.0.

CVSS

Version: 3.1
Vector: CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:N
Base score: 5.9

Exploitation probability (EPSS)

Probability of exploitation in the next 30 days: 0.33%
Percentile among all scored CVEs: 25
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.

ExploitationT1210 Exploitation of Remote Serviceslateral movement45 %
Primary impactT1078.004 Cloud Accountsstealth · persistence · privilege escalation · initial access75 %
Secondary impactT1550.001 Application Access Tokenlateral movement60 %

Acceso remoto a servicios con privilegios elevados (PR:H) para manipular configuración JWT y aceptar tokens expirados/inválidos, permitiendo suplantación de cuentas y bypass de autenticación.

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 Account Use Policies Application Developer Guidance Active Directory Configuration Vulnerability Scanning User Training

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-613, CWE-682

References

Raw JSON (NVD)

Show

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  "published": "2026-10-08T22:17:28.263",
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  "lastModified": "2026-10-09T16:17:23.590",
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