CVE-2026-42974: Windows Performance Monitor Integer Overflow Remote Code Execution Vulnerability

Technical summary

CVE-2026-42974 is an integer overflow vulnerability (CWE-190) in Windows Performance Monitor that permits remote code execution without authentication. The flaw arises from improper validation of numeric input, allowing an attacker to craft a network payload that causes integer wraparound. This results in memory corruption that can be leveraged to execute arbitrary code with the privileges of the Performance Monitor process. The attack vector is network-based, attack complexity is high, and no user interaction is required.

Business impact

Compromise of Windows systems running affected versions creates significant risk of data theft, system takeover, and lateral movement within corporate networks. Performance Monitor is a core Windows component, meaning any internet-facing or internally networked Windows device running a vulnerable version could become an attack vector. In environments where Performance Monitor is remotely accessible or monitored, the risk is amplified. Potential impacts include loss of confidentiality, integrity, and availability of critical business systems.

Affected systems

The vulnerability affects multiple versions of Windows 11 (23H2, 24H2, 25H2, 26H1) and Windows Server 2022 and Windows Server 2025. Both client and server operating systems are in scope. Organizations running these versions should prioritize assessment and patching. Verify exact patch availability against Microsoft security advisories, as not all versions may have patches released simultaneously.

Exploitability

While the vulnerability requires network access and high attack complexity (suggesting the attacker must overcome specific conditions or mitigations), it requires no authentication or user interaction. The CVSS 3.1 score of 8.1 (HIGH) reflects the combination of remote exploitability with full system compromise potential. However, the lack of any public exploit code in the CISA Known Exploited Vulnerabilities (KEV) catalog and the high attack complexity suggest weaponization barriers currently exist. Threat actors with sophisticated knowledge of Windows internals and memory layout randomization bypass techniques pose the greatest risk.

Remediation

Apply security patches from Microsoft as soon as they become available. Verify patch applicability to your specific Windows version and build number against official Microsoft security updates. Until patches are deployed, restrict network access to systems where Performance Monitor functionality is exposed or remotely callable, and enforce network segmentation to limit lateral movement if compromise occurs.

Patch guidance

Monitor Microsoft Security Update Guide and Windows Release Health pages for patches addressing CVE-2026-42974. Patches may be rolled out incrementally across different Windows versions and servicing channels. Test patches in a non-production environment before broad deployment. For Windows 11, verify which servicing versions (23H2, 24H2, 25H2, 26H1) receive patches and when. For Windows Server 2022 and 2025, coordinate patches with your release management and change control processes to minimize downtime.

Detection guidance

Monitor for unusual network traffic destined to Performance Monitor or the perfmon.exe process. Audit Event Viewer logs for unexpected elevation or code execution from Performance Monitor. Implement endpoint detection and response (EDR) tools tuned to flag abnormal process memory allocations or shellcode execution patterns originating from perfmon.exe. Hunt for failed integer operations or arithmetic exceptions in application event logs that may precede successful exploitation attempts.

Why prioritize this

HIGH priority due to CVSS 8.1 severity, network exploitability without authentication, and broad impact across both client and server Windows platforms in active use. The high attack complexity provides some operational friction, but the vulnerability still warrants immediate patch planning and deployment. Organizations with internet-facing Windows systems or those using Performance Monitor in monitoring infrastructure should prioritize this above lower-severity items.

Risk score, explained

The CVSS 3.1 score of 8.1 reflects a network-accessible vulnerability with no authentication requirement that can result in complete system compromise (high impact to confidentiality, integrity, and availability). The HIGH attack complexity prevents a perfect score but does not substantially reduce the practical risk, as targeted attackers with Windows internals expertise are likely to overcome those hurdles. The lack of KEV listing indicates no widespread public exploitation to date, but this may change as patches are released and reverse-engineering accelerates.

Frequently asked questions