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CVE-2026-120213— @fastify/http-proxy vulnerable to prefix escape via decoded route parameters

Quick assessment

Affected
@fastify/http-proxy @fastify/http-proxy
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

@fastify/http-proxy 是一个 Fastify 插件，用于将 HTTP 请求代理到配置前缀下的上游服务器。在 9.0.0 至 11.6.5 版本中，当应用程序使用参数化的 prefix 和 rewritePrefix 选项将客户端固定到某个上游路径时，该插件会将 URL 解码后的路由参数直接代入 rewritePrefix，而不会对其进行重新编码。因此，若某个参数值中编码了路径分隔符以及片段（fragment）或查询（query）分隔符，解码后这些字符会变为真实的路径分隔符和分隔符，从而注入额外的上

CVSS 9.1 · Critical
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I. Basic Information for CVE-2026-120213

Vulnerability Information
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Vulnerability Title
@fastify/http-proxy vulnerable to prefix escape via decoded route parameters
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
对路径名的限制不恰当(路径遍历)
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
@fastify/http-proxy @fastify/http-proxy 9.0.0 ~ 11.6.6 -

II. Public POCs for CVE-2026-120213

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III. Intelligence Information for CVE-2026-120213

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Vendor Advisories for CVE-2026-120213 (1)

IV. Related Vulnerabilities

Same product: @fastify/http-proxy
Same vendor: @fastify/http-proxy
Same weakness: CWE-22