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CVE-2026-16117

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

Published: Jul 18, 2026Updated: Jul 28, 2026 Sources: CVE List NVDCWE-20
10.0CRITICAL
NVD MITRE
EPSS Score
0.3%
Top 81.2%
CISA KEV
Not in KEV
Exploits
No Known Exploits
Remediation
Patch Available
Self-Check
Not available

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.

No summary for this CVE yet.

CVSS Vector Breakdown

AV:NAC:LPR:NUI:NS:CC:HI:HA:N
Exploitability
AV:NAttack Vector
Network
AC:LAttack Complexity
Low
PR:NPrivileges Required
None
UI:NUser Interaction
None
Scope
S:CScope
Changed
Impact
C:HConfidentiality
High
I:HIntegrity
High
A:NAvailability
None
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Weaknesses

CWE-20

Affected Products

@fastify/http-proxy
@fastify/http-proxy
fastify
oss-projectaka fastify-multipart, fastify/middie
fastify\/http-proxyLibrary
OSS Libraries / web-framework

Exploitability

Official Patch Available
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Attack Graph

Products CVE Techniques Tactics

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MITRE ATT&CK

1 technique
Initial Access
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References

https://github.com/fastify/fastify-http-proxy/security/advisories/GHSA-mx7v-qhg9-2mvv
github.com
https://cna.openjsf.org/security-advisories.html
cna.openjsf.org

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