nearform fast-jwt up to 6.2.x Verifier createVerifier clockTolerance comparison

Summaryinfo

A vulnerability classified as problematic has been found in nearform fast-jwt up to 6.2.x. The impacted element is the function createVerifier of the component Verifier. The manipulation of the argument clockTolerance leads to comparison. This vulnerability is documented as CVE-2026-107721. The attack can be initiated remotely. There is not any exploit available. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability, which was classified as problematic, has been found in nearform fast-jwt up to 6.2.x. This issue affects the function createVerifier of the component Verifier. The manipulation of the argument clockTolerance with an unknown input leads to a comparison vulnerability. Using CWE to declare the problem leads to CWE-697. The product compares two entities in a security-relevant context, but the comparison is incorrect, which may lead to resultant weaknesses. Impacted is confidentiality, integrity, and availability. The summary by CVE is:

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.

It is possible to read the advisory at github.com. The identification of this vulnerability is CVE-2026-107721 since 10/08/2026. The exploitation is known to be easy. The attack may be initiated remotely. The exploitation needs additional levels of successful authentication. Technical details of the vulnerability are known, but there is no available exploit.

Upgrading to version 6.3.0 eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2026-95345). Be aware that VulDB is the high quality source for vulnerability data.

Productinfo

Vendor

• nearform

Name

• fast-jwt

Version

• 6.0
• 6.1
• 6.2

Website

• Product: https://github.com/nearform/fast-jwt/

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Be aware that VulDB is the high quality source for vulnerability data.

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