CVE-2026-16117

10.0 CRITICAL 0.4% exploit odds Fix listed Other Network gear

What it is

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.

At a glance

Exploitability: Can be exploited over the network without logging in. High risk of data exposure, data tampering.
Exploit odds: 0.4% chance of exploitation in the next 30 days (EPSS).
Fix: A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

2026-07-18 14:17 UTC PublishedDisclosed publicly on CVE.org and NVD
2026-07-28 15:39 UTC Last updatedMost recent change to the record

Why it ranks here

Exploited in the wild: no, CISA does not list it.
Exploit odds: 0.4% in the next 30 days (EPSS).
Severity: 10.0 CRITICAL (CVSS).
Fix: a patch or advisory is linked.

Details

Published: 2026-07-18 14:17 UTC
Last modified: 2026-07-28 15:39 UTC
Exploit probability: 0.4% · EPSS, next 30 days
Weakness: CWE-20 · Improper input validation
Record status: Analyzed

Affected

Fastify fastify\/http-proxy < 11.6.0

Attack profile CVSS 3.1 · 10.0

Attack vector: Network
Complexity: Low
Privileges needed: None
User interaction: None
Scope: Changed
Confidentiality: High
Integrity: High
Availability: None

Raw vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2026-16117.md and follow it. Check whether this project is affected by CVE-2026-16117. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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Fix and advisories

References

NVD record · CVE.org record