CVE-2026-107275

MEDIUM 6.8

Published 2026-10-08 · Last modified 2026-10-08

@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.

NO EXPLOITATION SIGNALS

No known exploitation, public exploit, or elevated probability at this time. Track for changes.

Exploitation likelihood

0.3%chance of exploitation in 30 days · 24th percentile

○ In CISA KEV ○ Catalogued PoC

Impact if exploited

6.8CVSS 3.1 · MEDIUM

ConfidentialityHigh
IntegrityHigh
AvailabilityNone

What an attacker needs

✓Access: Reachable over the network — no local access needed
⚠Privileges: Requires a low-privilege account
✓User interaction: No user interaction needed
⚠Complexity: Needs a race window or specific setup

✓ lowers the bar for an attacker · ⚠ raises it

Proof of concept

No public PoC is currently catalogued.

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Tracked sources are checked daily for recent CVEs, including PoCs published after the original disclosure. A later release appears after a tracked source lists it and a refresh succeeds.

Data snapshot: 2026-10-26T13:52:32.101Z