Impact

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. Unfortunately, it is.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N

Patches

All releases after v4.3.1 include the fix.

Workarounds

There are no workaround available.

For more information

If you have any questions or comments about this advisory:

• Open an issue in fastify-reply-from
• Email us at hello@matteocollina.com

References

• GHSA-c4qr-gmr9-v23w
• fastify/fastify-http-proxy@02d9b43
• https://www.npmjs.com/package/fastify-http-proxy
• https://nvd.nist.gov/vuln/detail/CVE-2021-21322