Live › vulnerability › CVE-2026-120213
When an app uses parameterized prefix and rewritePrefix options, URL-decoded route parameters are inserted into the upstream path without re-encoding. A crafted parameter can inject path separators and query or fragment delimiters, letting an unauthenticated remote attacker reach upstream paths outside the intended prefix and bypass the enforced suffix, which can enable SSRF or authorization bypass in the proxied service.
Summary written from the sources below. Check the originals before acting.
First seen by InfraStack 2026-11-02 11:22 UTC. All times on this page are UTC.
Applications that use the @fastify/http-proxy plugin with parameterized prefix and rewritePrefix options to pin clients to a fixed upstream path. Exposure depends on the proxied upstream: SSRF or authorization bypass depends on what that service trusts. Apps that proxy with a fixed prefix and no route parameters in the rewrite are not described as affected.
No product ranges from the sources yet.
@fastify/http-proxy in the lockfile or with npm ls @fastify/http-proxy.prefix and rewritePrefix with route parameters in them.@fastify/http-proxy or later (affected: through ).11.6.69.0.011.6.5Each row is the first time that source carried this signal. The analyst’s rows are its own findings.
@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.
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