CVE-2026-86253Public exploitNetwork attack vector

Unauthenticated file read via decoded dot segments

Published Sep 6, 2026 · Updated Sep 10, 2026

Path traversal in UnJS H3 before 1.15.6 and 2.0.0-beta.0 through 2.0.1-rc.14 allows remote attackers to read server files. The serveStatic() function decodes percent-encoded dot segments from an unnormalized Node.js request pathname and passes resulting ../ sequences to filesystem callbacks without traversal validation. Exploitation requires a Node.js application to expose serveStatic(); the response can disclose any server file readable by that process.

CVSS severity8.2
High
EPSS probability0.43%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Path traversal in UnJS H3 before 1.15.6 and 2.0.0-beta.0 through 2.0.1-rc.14 allows remote attackers to read server files. The serveStatic() function decodes percent-encoded dot segments from an unnormalized Node.js request pathname and passes resulting ../ sequences to filesystem callbacks without traversal validation. Exploitation requires a Node.js application to expose serveStatic(); the response can disclose any server file readable by that process.

The record

CVE
CVE-2026-86253
Published
Sep 6, 2026
Updated
Sep 10, 2026
Vendor
UnJS
Product
H3
Classifications
CWE-22, T1190, T1005
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 6, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 10, 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 <1.15.6
  2. Affected versionversion=2.0.0-beta.0 <2.0.1-rc.15

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

UnJS · H3version=0 <1.15.6; version=2.0.0-beta.0 <2.0.1-rc.15

Published CVSS scores

5.9GitHubCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
8.2VulnCheckCVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA: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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

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
T1005Data from Local System

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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