CVE-2026-85124: high-severity vulnerability in @fastify/http-proxy
@fastify/http-proxy vulnerable to prefix escape via backslash dot-segments
Published
E-mail alert when it lands in KEV, gets a public PoC or its score goes up.
21Vexday Risk Score
No sign of exploitation. No public exploitation artifact known so far.
ssvc Trackcvss 7.5epss 0.7%
@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.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Affected products
@fastify/http-proxy · @fastify/http-proxyRelated CVEs — @fastify/http-proxy
In the same product, most dangerous first.
CVE-2026-120213CRITICAL@fastify/http-proxy vulnerable to prefix escape via decoded route parametersEPSS 0.7%CVE-2026-15631HIGH@fastify/http-proxy vulnerable to prefix escape via WebSocket path traversalEPSS 0.5%CVE-2026-120214MEDIUM@fastify/http-proxy vulnerable to prefix escape via percent-encoded backslash dot-segmentsEPSS 0.5%CVE-2026-16117CRITICAL@fastify/http-proxy vulnerable to prefix escape via URL-encoded charactersEPSS 0.4%