CVE-2026-62741 in Windows
Summary
by MITRE • 08/11/2026
Integer underflow (wrap or wraparound) 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 integer underflow condition within the Windows HTTP.sys kernel driver that enables local privilege escalation for authenticated attackers. The flaw occurs when the system processes HTTP requests and fails to properly validate integer values during buffer management operations, creating a scenario where arithmetic underflow can occur during memory allocation calculations. The vulnerability stems from inadequate input validation mechanisms within the http.sys component that handles Hypertext Transfer Protocol requests at the kernel level, specifically affecting how the system manages memory buffers for HTTP response processing.
The technical implementation of this vulnerability involves the exploitation of integer wraparound behavior in kernel-space memory management routines where an attacker can manipulate input parameters to cause arithmetic underflow conditions. When legitimate HTTP requests are processed through the http.sys driver, the system performs calculations to determine buffer sizes and memory allocation requirements. An attacker with local authenticated access can craft malicious HTTP requests that trigger these integer underflow scenarios, resulting in improper memory handling and potential code execution privileges. This behavior aligns with CWE-190, which specifically addresses integer overflow and underflow conditions in software systems.
The operational impact of this vulnerability extends beyond simple privilege escalation to potentially enable attackers to gain SYSTEM-level access on affected Windows systems. Local authenticated users can leverage this condition to execute arbitrary code with elevated privileges, effectively bypassing standard user access controls and security boundaries within the operating system. The exploitation process typically involves crafting specific HTTP requests that manipulate buffer size calculations, leading to memory corruption that can be leveraged for privilege elevation. This vulnerability particularly affects Windows systems running versions where the http.sys component has not been patched against this specific integer underflow condition.
Security professionals should note that this vulnerability operates within the ATT&CK framework under the Privilege Escalation tactic, specifically utilizing techniques related to kernel exploits and memory corruption. The attack vector requires local system access but does not necessitate network connectivity, making it particularly concerning for environments where local user accounts are present. Organizations should implement immediate patch management procedures to address this vulnerability, as Microsoft has released security updates that correct the integer underflow conditions in the http.sys driver. The mitigation strategy involves deploying the latest Windows security updates and implementing monitoring solutions to detect anomalous HTTP request patterns that might indicate exploitation attempts, while also ensuring proper access controls and user account management to limit local system access where possible.
This vulnerability demonstrates the critical importance of proper input validation and integer handling in kernel-level software components. The flaw highlights how seemingly benign operations like HTTP request processing can become attack vectors when proper boundary checks are absent from memory management routines. Security teams should prioritize this vulnerability for remediation due to its potential for local privilege escalation and the relatively low barrier to exploitation that authenticated local access provides. The integer underflow condition specifically affects systems where Windows HTTP.sys is actively utilized, making it particularly relevant for web server environments and systems that process HTTP traffic through kernel-level components.