CVE-2026-40400Network attack vector

Authenticated code execution via module help path traversal

Published Jul 14, 2026 · Updated Jul 14, 2026

Relative path traversal in Windows PowerShell on affected Windows releases allows remote authenticated users to execute code through help files. The module-help parser uses a user-supplied relative path in file operations without validating where it resolves. Exploitation requires an authenticated client to interact with a malicious link or file, and resulting code runs as the current user.

CVSS severity8.0
High
EPSS probability0.87%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Relative path traversal in Windows PowerShell on affected Windows releases allows remote authenticated users to execute code through help files. The module-help parser uses a user-supplied relative path in file operations without validating where it resolves. Exploitation requires an authenticated client to interact with a malicious link or file, and resulting code runs as the current user.

The record

CVE
CVE-2026-40400
Published
Jul 14, 2026
Updated
Jul 14, 2026
Vendor
Microsoft
Product
Windows Server 2019
Classifications
CWE-23, T1203, T1204.002
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Jul 14, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 14, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

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

  1. Affected versionversion=10.0.17763.0 <10.0.17763.9020

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Microsoft · Windows Server 2019version=10.0.17763.0 <10.0.17763.9020
Microsoft · Windows Server 2025 (Server Core installation)version=10.0.26100.0 <10.0.26100.33158
Microsoft · Windows 11, version 25H2version=10.0.26200.0 <10.0.26100.8875
Microsoft · Windows Server 2016 (Server Core installation)version=10.0.14393.0 <10.0.14393.9339
Microsoft · Windows 11, version 24H2version=10.0.26100.0 <10.0.26100.8875
Microsoft · Windows Server 2012 (Server Core installation)version=6.2.9200.0 <6.2.9200.26226
Microsoft · Windows Server 2012version=6.2.9200.0 <6.2.9200.26226
Microsoft · Windows 10 Version 21H2version=10.0.19044.0 <10.0.19044.7548
Microsoft · Windows Server 2016version=10.0.14393.0 <10.0.14393.9339
Microsoft · Windows 10 Version 22H2version=10.0.19045.0 <10.0.19045.7548
Microsoft · Windows Server 2012 R2 (Server Core installation)version=6.3.9600.0 <6.3.9600.23291
Microsoft · Windows Server 2019 (Server Core installation)version=10.0.17763.0 <10.0.17763.9020
Microsoft · Windows 11, version 26H1version=10.0.28000.0 <10.0.28000.2525
Microsoft · Windows 10 Version 1607version=10.0.14393.0 <10.0.14393.9339
Microsoft · Windows Server 2022version=10.0.20348.0 <10.0.20348.5386
Microsoft · Windows Server 2025version=10.0.26100.0 <10.0.26100.33158
Microsoft · Windows 10 Version 1809version=10.0.17763.0 <10.0.17763.9020
Microsoft · Windows Server 2012 R2version=6.3.9600.0 <6.3.9600.23291

Published CVSS scores

8.0MicrosoftCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H
7.0MicrosoftCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C

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 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-23Relative Path Traversal
T1203Exploitation for Client Execution
T1204.002User Execution Malicious File

Public exploit references

No public exploit references are available in this record.

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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