CVE-2026-85124Public exploitNetwork attack vectorHinoki check available

Internal endpoint disclosure via backslash path traversal

Published Sep 3, 2026 · Updated Sep 3, 2026

Path traversal in Fastify @fastify/http-proxy before 11.6.2 allows remote attackers to disclose internal endpoints via crafted HTTP paths. The plain HTTP handler forwards backslash dot-segments without the destination-boundary validation used for WebSockets, and URL resolution collapses them beyond rewritePrefix. Exposure requires an application to use prefix and rewritePrefix as an upstream path boundary; the reported consequence is disclosure, without integrity or availability impact.

CVSS severity7.5
High
EPSS probability0.55%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkAvailable
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Summary

What happened

Path traversal in Fastify @fastify/http-proxy before 11.6.2 allows remote attackers to disclose internal endpoints via crafted HTTP paths. The plain HTTP handler forwards backslash dot-segments without the destination-boundary validation used for WebSockets, and URL resolution collapses them beyond rewritePrefix. Exposure requires an application to use prefix and rewritePrefix as an upstream path boundary; the reported consequence is disclosure, without integrity or availability impact.

The record

CVE
CVE-2026-85124
Published
Sep 3, 2026
Updated
Sep 3, 2026
Vendor
Fastify
Product
@fastify/http-proxy
Classifications
CWE-22, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 3, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 3, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <11.6.2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Fastify · @fastify/http-proxyversion=0 <11.6.2

Published CVSS scores

7.5GitHub Security AdvisoryCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-22Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
T1190Exploit Public-Facing Application

Public exploit references

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Technologies

Your stack

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Your stack

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