CVE-2025-66415: Fastify Reply-From

Medium severity, CVSS 5.4. EPSS: 0.2% chance of exploitation in the next 30 days.

fastify-reply-from is a Fastify plugin to forward the current HTTP request to another server. Prior to 12.5.0, by crafting a malicious URL, an attacker could access routes that are not allowed, even though the reply.from is defined for specific routes in @fastify/reply-from. This vulnerability is fixed in 12.5.0.

Affected products

• Fastify Reply-From: up to and including 12.4.0

Published 2025-12-01. Last modified 2026-06-17.