CVE-2026-16117

CRITICALPre-NVD 10.010.0
EchelonGraph scoreLOW confidence

This critical-severity CVE scores 10.0 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit-prediction score not yet available (the EPSS model rescores nightly; freshly-published CVEs typically appear within 48 hours). GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: secondary
10.0
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: —CVSS: 10.0Exploit: NoneExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

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.

CVSS v3
10.0
EG Score
10.0(low)
EPSS
—
KEV
Not listed

Published

July 18, 2026

Last Modified

July 18, 2026

Advisory Details (2)

Auto-updated Jul 18, 2026
Patch available. Sources: github.
github Patch Available

@fastify/http-proxy vulnerable to prefix escape via URL-encoded characters · Advisory · fastify/fastify-http-proxy · GitHub

https://github.com/fastify/fastify-http-proxy/security/advisories/GHSA-mx7v-qhg9-2mvv
generic

Security Advisories | OpenJS Foundation CVE Numbering Authority

https://cna.openjsf.org/security-advisories.html

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 3× in last 7d / 3× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-07-18 16:08 UTCEG score recompute
  2. 2026-07-18 13:41 UTCEG score recompute
  3. 2026-07-18 13:39 UTCMITRE cvelistV5first tracked

Related CVEs(same CWE)

Frequently asked(4)

What is CVE-2026-16117?
CVE-2026-16117 is a critical vulnerability published on July 18, 2026. 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…
When was CVE-2026-16117 disclosed?
CVE-2026-16117 was first published in the National Vulnerability Database on July 18, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
What is the CVSS score of CVE-2026-16117?
CVE-2026-16117 has a CVSS v3 base score of 10.0 (NVD). The EG score is currently aggregating — additional source signals are being incorporated as they become available..
How do I remediate CVE-2026-16117?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-16117, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

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