CVE-2026-47291Public exploitNetwork attack vector

Kernel code execution via buffer-reference counter wraparound

Published Jun 9, 2026 · Updated Jun 9, 2026

Remote code execution in Windows HTTP.sys allows remote attackers to execute kernel-level code via crafted HTTPS requests. During HTTP/1.x header parsing, UlpParseNextRequest grows a buffer-reference array by five slots with unchecked 16-bit arithmetic; wraparound causes a 40-byte allocation followed by an approximately 524 KB copy. Reachability requires TLS, HTTP/1.x, and MaxRequestBytes of at least 262,144 bytes; exploitation can crash the host or execute code in the Windows kernel.

CVSS severity9.8
Critical
EPSS probability22.75%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Remote code execution in Windows HTTP.sys allows remote attackers to execute kernel-level code via crafted HTTPS requests. During HTTP/1.x header parsing, UlpParseNextRequest grows a buffer-reference array by five slots with unchecked 16-bit arithmetic; wraparound causes a 40-byte allocation followed by an approximately 524 KB copy. Reachability requires TLS, HTTP/1.x, and MaxRequestBytes of at least 262,144 bytes; exploitation can crash the host or execute code in the Windows kernel.

The record

CVE
CVE-2026-47291
Published
Jun 9, 2026
Updated
Jun 9, 2026
Vendor
Microsoft
Product
Windows Server 2019
Classifications
CWE-190, CWE-122, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 9, 2026CVE publishedPublication date reported by the CVE source.
  2. Jun 9, 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=10.0.17763.0 <10.0.17763.8880

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Microsoft · Windows Server 2019version=10.0.17763.0 <10.0.17763.8880
Microsoft · Windows Server 2025 (Server Core installation)version=10.0.26100.0 <10.0.26100.32995
Microsoft · Windows 11, version 25H2version=10.0.26200.0 <10.0.26200.8655
Microsoft · Windows Server 2016 (Server Core installation)version=10.0.14393.0 <10.0.14393.9234
Microsoft · Windows 11, version 24H2version=10.0.26100.0 <10.0.26100.8655
Microsoft · Windows Server 2012 (Server Core installation)version=6.2.9200.0 <6.2.9200.26132
Microsoft · Windows Server 2012version=6.2.9200.0 <6.2.9200.26132
Microsoft · Windows 10 Version 21H2version=10.0.19044.0 <10.0.19044.7417
Microsoft · Windows Server 2016version=10.0.14393.0 <10.0.14393.9234
Microsoft · Windows 10 Version 22H2version=10.0.19045.0 <10.0.19045.7417
Microsoft · Windows Server 2012 R2 (Server Core installation)version=6.3.9600.0 <6.3.9600.23228
Microsoft · Windows Server 2019 (Server Core installation)version=10.0.17763.0 <10.0.17763.8880
Microsoft · Windows 11, version 26H1version=10.0.28000.0 <10.0.28000.2269
Microsoft · Windows 11 Version 23H2version=10.0.22631.0 <10.0.22631.7219
Microsoft · Windows 10 Version 1607version=10.0.14393.0 <10.0.14393.9234
Microsoft · Windows Server 2022version=10.0.20348.0 <10.0.20348.5256
Microsoft · Windows Server 2025version=10.0.26100.0 <10.0.26100.32995
Microsoft · Windows 10 Version 1809version=10.0.17763.0 <10.0.17763.8880
Microsoft · Windows Server 2012 R2version=6.3.9600.0 <6.3.9600.23228

Published CVSS scores

9.8MicrosoftCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

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-190Integer Overflow or Wraparound
CWE-122Heap-based Buffer Overflow
T1190Exploit Public-Facing Application

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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