CVE-2026-16117: Impact: @fastify/http-proxy versions up to and including 11.5.0 fail to rewrite the request prefix when the pr

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CRITICAL 10.0REMOTEUPGRADE

CVE-2026-16117 is a critical-severity flaw (CVSS 10.0) affecting fastify\/http-proxy. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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 rewrit

Why this priority

Critical severity
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	10.0 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.4% (top 62%)
CISA exploited list	No
Weakness	CWE-20
Published	2026-07-18
Last modified	2026-07-28

Publisher (CNA): openjs · Vendor: fastify

Last updated 2026-07-28 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-07-18 14:17 UTCPublished CVE record published
2026-07-28 15:39 UTCUpdated Record last modified

fastify fastify\/http-proxy UPGRADE

Affected: < 11.6.0

Fixed in: 11.6.0

Safe to downgrade to: no unaffected older release

1. Check installed version

npm ls fastifyhttp-proxy

2. UPGRADE to 11.6.0

npm install fastifyhttp-proxy@">=11.6.0"

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-16117?

fastify\/http-proxy: upgrade to 11.6.0. Exact commands for each OS are on this page.

Is CVE-2026-16117 being exploited?

CVE-2026-16117 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-16117 affect?

CVE-2026-16117 affects fastify\/http-proxy. Severity is critical (CVSS 10.0). 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 f

How urgent is CVE-2026-16117?

Priority 50/100. Critical severity; Remotely exploitable, no login, no user action

Related CVEs

CVE-2026-33805 HIGH 8.6 UPGRADE UPGRADE @fastify/reply-from v12.6.1 and earlier and @fastify/http-proxy v11.4.3 and earlier process the client's Conne
CVE-2026-85124 HIGH 7.5 UPGRADE @fastify/http-proxy versions before 11.6.2 do not validate proxied HTTP request paths for backslash based dot-
CVE-2026-15631 HIGH 8.7 UPGRADE Impact: @fastify/http-proxy versions from 9.4.0 up to and including 11.5.0 fail to validate the resolved WebSo

References

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