CVE-2021-21322
fastify-http-proxy is an npm package which is a fastify plugin for proxying your http requests to another server, with hooks.
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (1.63%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
Description
fastify-http-proxy is an npm package which is a fastify plugin for proxying your http requests to another server, with hooks. 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 4.3.1.
- CVSS 3.1
- 9.8 CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- EPSS
- 1.63% probability · 76th percentile
- Public exploits
- None in Exploit-DB
- CISA KEV
- Not listed
- Weakness
- CWE-20
- Affected
- fastify-http-proxy project/fastify-http-proxy
- Source
- security-advisories@github.com
EPSS 1.6% since 26 October 2026; no change recorded yet. Points are recorded when the score first appears and whenever it moves by a percentage point or more.
References
- https://github.com/fastify/fastify-http-proxy/commit/02d9b43c770aa16bc44470edecfaeb7c17985016Patch, Third Party Advisory
- https://github.com/fastify/fastify-http-proxy/security/advisories/GHSA-c4qr-gmr9-v23wThird Party Advisory
- https://www.npmjs.com/package/fastify-http-proxyProduct, Third Party Advisory
- https://github.com/fastify/fastify-http-proxy/commit/02d9b43c770aa16bc44470edecfaeb7c17985016Patch, Third Party Advisory
- https://github.com/fastify/fastify-http-proxy/security/advisories/GHSA-c4qr-gmr9-v23wThird Party Advisory
- https://www.npmjs.com/package/fastify-http-proxyProduct, Third Party Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.