CVE-2026-42916: Windows NT Kernel Integer Overflow Privilege Escalation Vulnerability

Technical summary

CVE-2026-42916 is an integer overflow vulnerability (CWE-190) in the Windows NT OS Kernel that permits privilege escalation. The flaw occurs when an integer variable wraps around or exceeds its maximum value, leading to memory corruption or logic bypasses that an authenticated local user can leverage to execute code with elevated privileges. The CVSS 3.1 vector (AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H) indicates the attack is local, requires low complexity and low privilege, operates without user interaction, and has high impact on confidentiality, integrity, and availability of the affected system.

Business impact

This privilege escalation vulnerability poses a significant risk in environments where user isolation and least-privilege principles are critical. A compromised standard user account can become a gateway to full system compromise, allowing attackers to install malware, modify system configurations, exfiltrate sensitive data, or disable security controls. In enterprise deployments with Windows Server infrastructure, this creates a path for lateral movement and organizational breach. The broad version coverage—spanning multiple Windows 10 and 11 releases plus Server 2012–2025—means patching is necessary across most Windows deployments to adequately reduce risk.

Affected systems

The vulnerability affects Microsoft Windows 10 (versions 1607, 1809, 21H2, and 22H2), Windows 11 (versions 23H2, 24H2, 25H2, and 26H1), and Windows Server editions from 2012 through 2025. Organizations running any of these supported versions should assume systems are potentially vulnerable until patched. Systems running older unsupported versions (such as Windows 7 or early Windows Server releases) are not listed but may carry similar or related flaws depending on vendor advisories.

Exploitability

Exploitation requires local system access and the ability to execute code with standard user privileges. The low attack complexity and absence of user interaction requirements mean that once a foothold is established on a system, leveraging this flaw to escalate privileges is relatively straightforward for a competent attacker. This makes it especially dangerous in multi-user environments, containerized deployments, or scenarios where supply-chain compromises or phishing have already delivered initial access. The vulnerability is not currently tracked as exploited in the wild according to available KEV data, but the technical simplicity and broad impact suggest it warrants rapid remediation.

Remediation

Organizations must apply security updates from Microsoft as soon as they are released and tested in their environment. Patches should be validated in a staging environment before broad deployment. In parallel, operational controls such as disabling unnecessary user accounts, enforcing code integrity policies, and restricting local logon permissions can reduce the attack surface. Monitoring for suspicious privilege escalation attempts and enforcing application whitelisting on critical systems can help detect exploitation attempts.

Patch guidance

Consult Microsoft's official security advisories and the Windows Update service for patched versions specific to your system version and build. Organizations using Windows Server should coordinate patching across domain-joined systems using WSUS or similar patch management solutions. Test patches in a non-production environment to ensure compatibility with third-party drivers and applications before enterprise rollout. Priority should be given to systems that host sensitive data or serve critical business functions.

Detection guidance

Monitor Windows event logs for unusual privilege escalation attempts, particularly in the Security log for failed and successful token elevation events (Event ID 4672, 4673). Watch for suspicious kernel-mode activity or unexpected system calls that may indicate integer overflow exploitation. Endpoint detection and response (EDR) tools configured to alert on privilege escalation patterns and kernel memory access anomalies will help identify exploitation attempts. Process monitoring should flag attempts to create high-privilege processes from standard user contexts without administrative consent dialogs.

Why prioritize this

With a CVSS score of 7.8 (HIGH severity), broad version coverage across both client and server operating systems, and a straightforward attack path requiring only local access and standard privileges, this vulnerability merits immediate remediation. Although not yet observed in active exploitation, the combination of ease of exploitation, wide blast radius, and direct impact on system security boundaries makes it a priority for all organizations running affected Windows versions. Delaying patching increases organizational risk significantly.

Risk score, explained

The score of 7.8 reflects the high severity due to: (1) local attack vector requiring only standard user access—common in enterprise environments; (2) low complexity exploitation—the integer overflow mechanics are well-understood; (3) high impact on all three CIA triad dimensions—a privilege escalation opens the door to data theft, malware installation, and denial of service; (4) broad affected version base spanning multiple client and server product lines; and (5) the absence of complex environmental factors or user interaction. The score does not include CVSS temporal adjustments; actual risk may vary based on whether exploits become publicly available or adoption of patches.

Frequently asked questions