CVE-2026-62739 in Windows
Summary
by MITRE • 08/11/2026
Heap-based buffer overflow in Windows HTTP.sys allows an authorized attacker to elevate privileges locally.
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Analysis
by VulDB Data Team • 08/11/2026
This vulnerability represents a critical heap-based buffer overflow within the Windows HTTP.sys kernel driver that enables local privilege escalation for authenticated attackers. The flaw exists in how the HTTP.sys component processes certain network requests, specifically when handling malformed HTTP headers or request structures that trigger improper memory allocation and copying operations. When an authenticated user submits maliciously crafted HTTP requests to a system running the affected HTTP.sys driver, the vulnerability manifests through heap corruption that can be exploited to execute arbitrary code with kernel-level privileges. The technical implementation involves the driver's failure to properly validate input lengths during HTTP request processing, allowing attackers to overwrite adjacent heap memory regions. This vulnerability directly maps to CWE-121 Heap-based Buffer Overflow, which is classified as a critical weakness in memory safety. The operational impact extends beyond simple privilege escalation as it provides attackers with complete system compromise capabilities, enabling them to bypass standard security controls, access sensitive data, and establish persistent backdoors. Attackers can leverage this vulnerability through local network access or by exploiting other initial access vectors that allow them to execute code on the target system. The ATT&CK framework categorizes this as privilege escalation technique T1068, where an attacker uses a kernel-level vulnerability to gain SYSTEM privileges. Microsoft has classified this issue with high severity due to its potential for local privilege escalation and the relatively straightforward exploitation process that requires only authenticated access. Organizations should prioritize immediate patching of affected Windows versions and implement network segmentation to limit potential attack surfaces. Additional mitigations include disabling unnecessary HTTP services, monitoring for anomalous HTTP request patterns, and applying principle of least privilege configurations to reduce the impact if exploitation occurs. The vulnerability demonstrates how kernel-level flaws in system services can provide attackers with the most privileged execution context available on Windows systems, making it a prime target for advanced persistent threat actors seeking complete system compromise.