Description
fastify-reply-from is an npm package which is a fastify plugin to forward the current http request to another server. In fastify-reply-from before version 4.0.2, by crafting a specific URL, it is possible to escape the prefix of the proxied backend service. If the base url of the proxied server is "/pub/", a user expect that accessing "/priv" on the target service would not be possible. In affected versions, it is possible. This is fixed in version 4.0.2.
Remediation
References
https://github.com/fastify/fastify-reply-from/commit/dea227dda606900cc01870d08541b4dcc69d3889
https://github.com/fastify/fastify-reply-from/security/advisories/GHSA-qmw8-3v4g-gwj4
https://www.npmjs.com/package/fastify-reply-from