Description

Heap-based buffer overflow in Windows HTTP.sys allows an authorized attacker to elevate privileges locally.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "7.8",
  "pubDate": "2026-08-11T17:18:25.037Z",
  "pubdate": "2026-08-11T17:18:25.037Z",
  "executiveSummary": "This vulnerability is classified as a heap-based buffer overflow affecting the Windows HTTP.sys component, a core operating system driver responsible for processing Hypertext Transfer Protocol requests. The primary security impact of successful exploitation is local privilege escalation, which allows an attacker to execute arbitrary code with elevated system privileges.\nThe affected system is the Microsoft Windows operating system utilizing the HTTP.sys driver for web and network request handling. Risk implications are severe, as an authenticated attacker who has already established initial access to the local system can leverage this kernel-mode memory corruption flaw to bypass security boundaries, compromise the underlying operating system kernel, and achieve full administrative control over the targeted host.\nAttacker capabilities require local execution context, meaning the adversary must already possess valid credentials or local code execution capabilities on the target machine. Furthermore, exploitation requirements dictate that the attacker must be authorized to interact with the local environment, though the exact execution parameters depend on the specific memory management handling within the vulnerable driver. Because HTTP.sys operates at the kernel level, successful exploitation invalidates standard user-mode isolation protections, leading directly to complete system compromise.",
  "technicalDetails": "The root cause of the vulnerability resides in memory management deficiencies within the HTTP.sys kernel-mode driver, specifically during the handling of dynamic heap allocations and buffer size calculations. When processing malformed or oversized requests, the affected component fails to accurately validate input boundaries before writing data into a pre-allocated heap buffer.\nThe vulnerable component is the Windows HTTP.sys driver, which parses incoming HTTP requests at the kernel level. Because this component runs in ring 0, any memory corruption occurring within its heap space directly impacts kernel stability and integrity. The vulnerability affects the standard heap management routines utilized by the driver when storing state data, request headers, or URI paths.\nThe exploitation method relies on heap-based buffer overflow mechanics. An authorized local attacker crafts a specialized input sequence designed to exceed the allocated boundaries of a heap chunk managed by HTTP.sys. By systematically sending this crafted request to the local HTTP stack, the attacker forces a heap overflow, overwriting adjacent memory structures, function pointers, or object control blocks located on the kernel heap.\nThe step-by-step attack flow proceeds as follows: First, the local attacker establishes execution within a standard user-mode context and authenticates or interacts locally with the system. Second, the attacker formulates a payload engineered to trigger the buffer overflow condition within the HTTP.sys allocation routine. Third, the attacker transmits the malformed request via local inter-process communication or local network sockets bound to the HTTP stack. Fourth, HTTP.sys receives the request and commits the oversized data into the heap without adequate bounds checking. Fifth, the overflow corrupts adjacent kernel heap metadata or critical function pointers. Finally, the attacker redirects execution flow to injected shellcode or kernel-level primitives, culminating in the elevation of the current process token to SYSTEM privileges.\nAuthentication requirements specify that the attacker must be authorized to interact with the local system, though specific administrative privileges are not required to initiate the attack vector. Privilege requirements are limited to local access, but successful execution transitions the attacker to high-privilege kernel execution (NT AUTHORITY\\SYSTEM). Network exposure for this specific local vector is restricted to local interfaces, precluding remote unauthenticated exploitation unless combined with a separate remote code execution vulnerability.\nPost-exploitation impact includes complete loss of confidentiality, integrity, and availability of the host. With kernel-level privileges, the attacker can disable security software, install persistent rootkits, intercept all network traffic, and manipulate operating system mechanisms without restriction."
}