{"id":"CVE-2026-120213","published":"2026-11-02T11:17:31.137","lastModified":"2026-11-02T17:17:39.467","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.","cvssScore":9.1,"cvssSeverity":"CRITICAL","cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N","cwes":["CWE-22","CWE-436"],"vendors":[],"products":[],"references":[{"url":"https://cna.openjsf.org/security-advisories.html","tags":[]},{"url":"https://github.com/fastify/fastify-http-proxy/security/advisories/GHSA-h3vp-4jfr-v364","tags":[]}],"exploitRefs":[{"url":"https://github.com/fastify/fastify-http-proxy/security/advisories/GHSA-h3vp-4jfr-v364","tags":[]}],"hasPoc":true,"ai":{"summary":"The @fastify/http-proxy plugin incorrectly decodes URL parameters in rewritePrefix without re-encoding them, allowing attackers to inject path separators and query delimiters via encoded characters (e.g., %2f) to bypass intended upstream path restrictions and access unintended endpoints.","exploitability":"Exploitation is straightforward for unauthenticated remote attackers; no user interaction or special privileges are required, and public exploits exist.","blast_radius":"Successful exploitation enables server-side request forgery (SSRF) or authorization bypass in the upstream service, potentially exposing sensitive internal resources or data.","remediation":"Upgrade @fastify/http-proxy to version 11.6.6 or later.","detection":"Look for upstream requests where the path contains unexpected segments that correspond to decoded URL-encoded characters (e.g., %2f appearing as / in the final upstream path), especially when such paths deviate from the configured rewritePrefix pattern; logs from the proxy or upstream server may show anomalous request paths.","tags":["path-traversal","ssrf","auth-bypass","web","nodejs"],"model":"garnet-coder","analyzedAt":"2026-11-03T09:56:20.899Z"}}