CVE-2025-24983

What it actually does

CVE-2025-24983 is a use-after-free vulnerability in the Windows Win32 Kernel Subsystem. A local, authenticated attacker who can execute code on a vulnerable Windows system can trigger unsafe reuse of freed kernel memory to elevate privileges. Successful exploitation can allow code running with low or standard user privileges to gain higher local privileges, potentially up to SYSTEM-level execution depending on exploit reliability and target conditions. Because the flaw is in a Windows kernel-adjacent subsystem, exploitation is typically used after initial access to break out of user-level constraints rather than as an internet-facing entry point.

Why it matters to the business

This vulnerability increases the impact of any successful compromise of a Windows endpoint or server because an attacker with limited access may be able to take full control of the local system. It can enable credential theft, disabling of security tools, persistence, lateral movement, tampering with business data, and deployment of follow-on malware. Although the EPSS score is low, the vulnerability is listed in CISA KEV and has active in-the-wild exploitation, making remediation urgent. The CISA remediation due date was 2025-04-01, so any remaining unpatched Windows systems should be treated as overdue risk.

How an attack unfolds

An attacker first obtains local code execution on a vulnerable Windows system through phishing, malware, stolen credentials, exploitation of another vulnerability, or abuse of legitimate remote access. Once running as a low-privileged or constrained user, the attacker launches an exploit that interacts with the Win32 Kernel Subsystem in a way that causes a kernel object or memory structure to be freed and then reused while still referenced. By carefully influencing memory layout, the attacker can redirect execution or corrupt security-relevant kernel state to raise the privileges of the attacking process. After privilege escalation, the attacker commonly spawns or injects into a high-privilege process, dumps credentials, disables endpoint defenses, installs persistence, or moves laterally. Public reporting and KEV inclusion indicate exploitation has occurred in the wild; therefore, investigation should focus on systems where untrusted local execution occurred before patching.

How to fix it

Apply the Microsoft security update that fixes CVE-2025-24983 on all affected Windows systems. In the absence of product-specific fixed versions in the input, organizations should deploy the March 2025 Microsoft security updates or any later cumulative updates applicable to their supported Windows versions. Prioritize internet-managed endpoints, systems used by privileged users, remote access hosts, jump boxes, domain controllers, servers handling sensitive data, and endpoints with evidence of malware or unauthorized local execution. Where immediate patching is not possible, reduce local code execution risk by limiting interactive logons, removing unnecessary local administrator rights, enforcing application control, hardening endpoint protection, blocking untrusted script execution, and monitoring for suspicious privilege escalation behavior. Unsupported Windows versions should be upgraded or isolated because cumulative fixes may not be available or reliable.

How to confirm the fix worked

Confirm remediation by verifying that each Windows system has installed the applicable March 2025 or later cumulative security update from Microsoft. Use centralized patch management, vulnerability scanning, Microsoft Update history, and system inventory to identify systems missing the relevant update. Validate that the operating system build number and installed hotfix level meet or exceed the patched baseline for the specific Windows release. For high-risk assets, perform an authenticated vulnerability scan after patch deployment and confirm the finding is no longer reported. Because this is a local privilege escalation flaw, external network scans alone are insufficient; validation must include authenticated host-level checks.

Typical attack path

1. Gain initial access to a Windows workstation or server using phishing, malware, stolen credentials, exposed remote access, or another exploit.
2. Execute code locally under a low-privileged, standard, or otherwise constrained user context.
3. Trigger the Win32 Kernel Subsystem use-after-free condition to manipulate freed kernel memory.
4. Escalate the attacker-controlled process to elevated local privileges, potentially SYSTEM.
5. Use elevated privileges to disable defenses, access protected files, dump credentials, create persistence, or launch additional tools.
6. Move laterally or perform the attacker’s primary objective, such as data theft, domain escalation, sabotage, or malware deployment.

How to detect it

There are no universal, CVE-specific log strings that reliably prove exploitation of this kernel privilege escalation vulnerability. Detection should focus on behavior before and after a suspected local privilege escalation. Review EDR telemetry, Windows Security logs, Sysmon logs, PowerShell logs, application control logs, and crash dump data from vulnerable systems, especially during periods before patching. Look for a low-privileged user process unexpectedly spawning SYSTEM-level processes, creating services, modifying scheduled tasks, disabling security controls, dumping credentials, or accessing LSASS. Investigate suspicious process ancestry where user-writable paths, temporary directories, downloaded files, scripts, or unknown binaries are followed by elevated process creation. Review Windows events for new service creation, scheduled task registration, security policy changes, audit log clearing, Defender tampering, and unexpected local administrator group changes. Kernel exploitation may also cause instability, so correlate suspicious activity with application crashes, bugchecks, memory dumps, or endpoint protection alerts involving win32k, GUI subsystem activity, or abnormal kernel memory behavior. Because the vulnerability is known to be exploited in the wild and is KEV-listed, any unpatched system with unexplained privilege changes or post-exploitation behavior should be considered for deeper forensic review.

What your security team should do

• Treat this as a priority remediation item because it is in CISA KEV and has active in-the-wild exploitation despite a relatively low EPSS score.
• Identify all Windows systems that have not received the March 2025 or later cumulative security updates and patch them urgently.
• Prioritize systems where local compromise would have high impact, including privileged user workstations, servers, domain infrastructure, remote access systems, and security administration hosts.
• Hunt for signs of local privilege escalation on Windows systems that were unpatched after publication on 2025-03-11 or after the CISA due date of 2025-04-01.
• Review endpoint detections for suspicious transitions from low-privileged user activity to SYSTEM-level processes, especially when followed by credential access or security tool tampering.
• Limit local administrator rights and enforce least privilege to reduce the value of successful exploitation.
• Ensure EDR, Windows event logging, PowerShell logging, process creation logging, and security audit policies are enabled and retained long enough to investigate historical exploitation.
• For systems that cannot be patched promptly, isolate them, restrict interactive access, and apply application control to prevent untrusted binaries or scripts from running.