CVE-2026-62811 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 the way the HTTP protocol stack processes certain network requests, specifically when handling malformed HTTP headers or request structures that exceed allocated memory boundaries. When an attacker crafts malicious HTTP traffic or exploits existing connections with crafted payloads, the vulnerable code fails to properly validate input lengths before copying data into heap-allocated buffers, resulting in memory corruption that can be exploited to execute arbitrary code with kernel-level privileges.
The technical implementation of this vulnerability stems from inadequate bounds checking within the Windows HTTP.sys driver component which handles HTTP protocol processing at the kernel level. Attackers who possess valid user credentials on a target system can leverage this flaw by establishing specific HTTP connections or manipulating existing ones to trigger the buffer overflow condition. The heap corruption occurs when the driver processes HTTP requests containing oversized headers or malformed data structures that exceed the expected buffer sizes, causing adjacent memory to be overwritten and potentially allowing for code execution in kernel space.
From an operational perspective, this vulnerability presents significant risk as it requires only local authentication credentials rather than network-level access, making it particularly dangerous in environments where user accounts may have elevated privileges or where attackers can obtain legitimate credentials through social engineering or other means. The privilege escalation occurs because the HTTP.sys driver operates with high-privilege kernel access rights, meaning successful exploitation allows attackers to gain SYSTEM level control over the affected Windows system. This makes the vulnerability particularly attractive for attackers seeking persistent access to compromised systems.
The impact of this vulnerability extends beyond simple privilege escalation as it can enable further attack vectors including lateral movement within networks, data exfiltration, and establishment of backdoors. Security professionals should note that this flaw aligns with common attack patterns documented in the attack tactics and techniques framework, particularly those involving privilege escalation through kernel-level vulnerabilities. The weakness maps directly to CWE-121 heap-based buffer overflow conditions where insufficient bounds checking allows attackers to overwrite adjacent memory locations, potentially leading to arbitrary code execution. Mitigation strategies should include immediate deployment of Microsoft security patches, network segmentation to limit local access, and implementation of monitoring solutions to detect anomalous HTTP traffic patterns that might indicate exploitation attempts. Organizations should also consider implementing principle of least privilege controls and regularly audit user account permissions to minimize potential impact from successful exploitation of this vulnerability.