CVE-2026-107275

Medium

Description

@fastify/jwt is a JSON Web Token plugin for the Fastify web framework. In versions before 10.2.3, a time span passed to expiresIn, notBefore, or maxAge that the plugin's parser cannot read, such as a compound span, a month unit, an ISO 8601 duration, a decimal comma, or a value with surrounding whitespace, is silently dropped instead of refused. On the signing path this produces a token with no expiration claim that never expires, and on the verification path a configured maxAge stops being enforced, so a token that should be rejected for age is accepted. The issue is fixed in @fastify/jwt 10.2.3, and users should upgrade to 10.2.3 or later. As a workaround, pass these options as a number of seconds, or verify that any time-span string parses to a finite value before relying on it.

SeverityMedium
CVSS6.8
Exploit probability—
Product@fastify/jwt
PublishedOct 8, 2026
First seenOct 8, 2026

How to fix

Update
  • @fastify/jwt @fastify/jwt10.2.3 or later

Affected products

ProductAffected versionsFixed in
@fastify/jwt @fastify/jwtv < 10.2.310.2.3

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