PT-2026-48025 · Microsoft · Iis+4
CVE-2026-47291
·
Published
2026-06-09
·
Updated
2026-07-16
CVSS v3.1
10
Critical
| Vector | AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H |
Name of the Vulnerable Software and Affected Versions
Windows HTTP.sys (affected versions not specified)
Description
An integer overflow or wraparound exists in the Windows HTTP Protocol Stack kernel-mode driver (HTTP.sys). The issue occurs during the dynamic expansion of the buffer array in the
UL REQUEST BUFFER structure due to an overflow in the 16-bit capacity field when handling HTTP/1.x requests over TLS. A remote unauthenticated attacker can trigger a kernel heap overflow of more than 500 KB by sending a specially crafted HTTP request where each header line is encapsulated in a separate TLS record, provided that the MaxRequestBytes registry value is greater than or equal to 262144 and the request contains tens of thousands of header lines. Because HTTP.sys operates in kernel mode, successful exploitation allows the attacker to execute arbitrary code with SYSTEM privileges. This flaw specifically affects HTTP/1.x over HTTPS; HTTP/2 and HTTP/3 are not affected.Recommendations
Deploy the June 2026 Microsoft Patch Tuesday cumulative security updates across all Windows Server and workstation endpoints.
Limit the
MaxRequestBytes parameter registry value under HKLMSYSTEMCurrentControlSetServicesHTTPParameters to enforce safe constraints on inbound HTTP requests.Fix
RCE
DoS
Integer Overflow
Heap Based Buffer Overflow
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Related Identifiers
Affected Products
Iis
Windows
Windows 10
Windows 11
Windows Server