CVE-2026-49160: HTTP.sys Denial of Service Vulnerability

Overview

Severity
High (CVSS 7.5)
CVSS Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H/E:U/RL:O/RC:C
Category
Denial of Service
Exploit Status
Not Exploited
Exploitation Likelihood
More Likely
Publicly Disclosed
Yes
Patch Tuesday
2026-Jun
Released
2026-06-09

Description

Uncontrolled resource consumption in HTTP/2 allows an unauthorized attacker to deny service over a network.

FAQ

What actions should I take to help protect my devices from this vulnerability? Install the June 2026 Windows security updates listed in the Security Updates table. These updates enable the protections Microsoft released for this CVE. As part of these updates, Microsoft also introduced a new MaxHeadersCount registry setting. This setting allows you to limit the number of headers included in HTTP/2 and HTTP/3 requests that are accepted by the HTTP server. For more information, see KB5102602.

Affected Products (26)

Windows

  • Windows Server 2019 (Server Core installation)
  • Windows 10 Version 1809 for 32-bit Systems
  • Windows 10 Version 21H2 for 32-bit Systems
  • Windows 10 Version 21H2 for ARM64-based Systems
  • Windows 10 Version 21H2 for x64-based Systems
  • Windows Server 2022 (Server Core installation)
  • Windows Server 2025 (Server Core installation)
  • Windows 11 Version 25H2 for ARM64-based Systems
  • Windows 11 Version 25H2 for x64-based Systems
  • Windows 11 Version 23H2 for ARM64-based Systems
  • Windows 11 Version 23H2 for x64-based Systems
  • Windows 11 Version 24H2 for ARM64-based Systems
  • Windows 11 Version 24H2 for x64-based Systems
  • Windows 11 version 26H1 for x64-based Systems
  • Windows 11 Version 26H1 for ARM64-based Systems
  • Windows Server 2025
  • Windows 10 Version 1607 for 32-bit Systems
  • Windows 10 Version 1607 for x64-based Systems
  • Windows Server 2016
  • Windows Server 2016 (Server Core installation)
  • Windows 10 Version 1809 for x64-based Systems
  • Windows Server 2022
  • Windows Server 2019

ESU

  • Windows 10 Version 22H2 for x64-based Systems
  • Windows 10 Version 22H2 for ARM64-based Systems
  • Windows 10 Version 22H2 for 32-bit Systems

Security Updates (8)

Acknowledgments

Quang Luong of Calif.io in collaboration with Codex with <a href="https://www.calif.io/">Calif.io</a>

Revision History

  • 2026-06-09: Information published.