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CVE-2026-16117

Severity
CRITICAL
CVSS
10.0
EPSS
0.00269
Risk score
40.09
CISA KEV
No
PoC
No
Published
2026-07-18
Modified
2026-07-20
First seen
2026-08-05
Aliases
EUVD-2026-45379
Products
@fastify/reply-from:@fastify/http-proxy 0 <11.6.0, fastify:fastify\/http-proxy
Sources
nvd CVE-2026-16117
euvd EUVD-2026-45379

Description

Impact: @fastify/http-proxy versions up to and including 11.5.0 fail to rewrite the request prefix when the prefix segment is URL-encoded. Fastify's router URL-decodes paths for route matching, but request.url retains the original encoded form, and the prefix-rewrite step uses a literal string replace against the decoded prefix. A request that encodes one or more characters of the configured prefix therefore matches the route but skips the rewrite, so the raw encoded path is forwarded to the upstream unchanged. The upstream then decodes the path and serves it, letting an attacker reach upstream paths that the proxy was configured to hide via rewritePrefix, including internal or administrative endpoints. Patches: upgrade to @fastify/http-proxy 11.6.0. Workarounds: none.

References