CVE-2026-120213 @fastify/http-proxy vulnerable to prefix escape via decoded route parameters
- Exploited in the wild
- Not known
- Fix
- None listed
What is CVE-2026-120213?
CVE-2026-120213 is a critical vulnerability in @fastify/http-proxy, published on 2 Nov 2026.
Official description
@fastify/http-proxy is a Fastify plugin that proxies HTTP requests to an upstream server under a configured prefix. In versions 9.0.0 through 11.6.5, when an application uses parameterized prefix and rewritePrefix options to pin clients to a fixed upstream path, the plugin substitutes URL-decoded route parameters into rewritePrefix without re-encoding them. A parameter value that encodes a path separator together with a fragment or query delimiter therefore decodes into real separators and delimiters that inject extra upstream path segments and strip the mandatory suffix the rewritePrefix was meant to enforce, without using any dot-dot traversal. An unauthenticated remote attacker can use this to reach upstream locations outside the intended prefix, leading to path-restriction bypass and, depending on the upstream, server-side request forgery or authorization bypass in the proxied service. The issue is fixed in @fastify/http-proxy 11.6.6, and users should upgrade to 11.6.6 or later. There is no workaround other than upgrading.
Which versions are affected by CVE-2026-120213?
How do I fix CVE-2026-120213?
No fix has been published for CVE-2026-120213 yet. Limit exposure of the affected software until one is available.
Is CVE-2026-120213 being exploited?
There is no known exploitation of CVE-2026-120213 in the wild and no public exploit code.
Sources
Also known as GHSA-h3vp-4jfr-v364.