CVE-2025-66415: fastify fastify-reply-from Confused Deputy

Vulnerability summary

CVE-2025-66415 is a medium (CVSS 6.9) Confused Deputy vulnerability in fastify fastify-reply-from. EPSS estimates a 0.18% chance of exploitation in the next 30 days, higher than 7% of scored vulnerabilities.

Timeline

1. 01-12-2025
   PublishedVulnerability first disclosed.
2. 02-12-2025
   Last modifiedVulnerability information updated.

Description

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.

• CWE-441Unintended Proxy or Intermediary ('Confused Deputy')The product receives a request, message, or directive from an upstream component, but the product does not sufficiently preserve the original source of the request before forwarding the request to an external actor that is outside of the product's control sphere. This causes the product to appear to be the source of the request, leading it to act as a proxy or other intermediary between the upstream component and the external actor.