Fastify Fastify\/Http-Proxy
CVE-2026-85124
@fastify/http-proxy versions before 11.6.2 do not validate proxied HTTP request paths for backslash based dot-segments before forwarding them to the configured upstream. The plain HTTP request handler skips the destination validation that the WebSocket path performs, and the underlying reply-from library only rejects forward-slash traversal, so a request containing backslash dot-segments can escape the boundary set by the prefix and rewritePrefix options. An unauthenticated network attacker can use this to reach upstream paths that were meant to stay hidden behind the proxy, resulting in disclosure of internal endpoints. This is a path traversal issue (CWE-22). Users should upgrade to @fastify/http-proxy 11.6.2 or later.
What this means for your business
- It affects Fastify\/Http-Proxy. It matters if your company, or a supplier that handles your data, runs it.
- An attacker can use it remotely, over a network, without a login, and without anyone at your company clicking anything.
- FIRST's prediction model gives it a 0.6% chance of attack attempts being seen in the next 30 days, ranking above 44% of all known flaws.
What to do
- 1Check whether your company or your suppliers run Fastify\/Http-Proxy, and which version. The affected versions are listed further down this page.
- 2If you do, apply the vendor's fix. A patch or vendor advisory has been published.
Fastnexa security experts
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Scoring
- CVSS
- 7.5 (v3.1)
- Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N- Weakness
- CWE-22
- Assigned by
- ce714d77-add3-4f53-aff5-83d477b104bb
Dates
- Published
- 2026-09-03
- Last modified
- 2026-09-09
- Sources
- NVD
Affected products
- Fastify Fastify\/Http-Proxy- 11.6.2
As listed in the NVD configuration data. Not a statement about your estate.