Windows DWM 0-Day Vulnerability Allows Attackers to Escalate Privileges

Microsoft has patched a critical zero-day vulnerability in the Windows Desktop Window Manager (DWM) Core Library, tracked as CVE-2025-30400, which was actively exploited in the wild to grant attackers SYSTEM-level privileges on affected systems.

The flaw, disclosed as part of Microsoft’s May 2025 Patch Tuesday, underscores the persistent risks posed by privilege escalation bugs in widely deployed Windows components.

CVE-2025-30400 is classified as an “Elevation of Privilege” vulnerability stemming from a “use-after-free” memory corruption issue in the DWM Core Library.

This weakness, cataloged under CWE-416, allows an authorized attacker to execute code with SYSTEM privileges-the highest level of access on Windows systems-by exploiting improper memory management within the DWM process.

According to Microsoft, the vulnerability can be leveraged locally by an attacker who already has access to the target machine. Successful exploitation enables the attacker to bypass standard security boundaries, potentially allowing them to install malicious software, modify system settings, or access sensitive data without detection.

Exploitation and Impact

Microsoft confirmed that CVE-2025-30400 had been actively exploited before a patch was made available, making it a genuine zero-day threat.

Although the vulnerability was not publicly disclosed prior to patching, evidence of exploitation was detected in the wild, prompting Microsoft to urge immediate action from users and administrators.

“Use after free in Windows DWM allows an authorized attacker to elevate privileges locally,” Microsoft stated in its advisory. The company attributed the discovery of this flaw to its own Threat Intelligence Center, highlighting the ongoing efforts to monitor and respond to emerging threats.

Attackers exploiting this bug could gain SYSTEM privileges, granting them full control over the compromised device. This level of access is particularly dangerous, as it allows for persistent and stealthy attacks that can evade traditional security measures.

The fix for CVE-2025-30400 was released on May 13, 2025, as part of a broader security update that addressed a total of 72 to 83 vulnerabilities, including five zero-days that were actively exploited.

Microsoft classified the severity of this vulnerability as “Important” and assigned it a CVSS score of 7.8, reflecting its significant risk to enterprise and consumer systems.

Security experts and Microsoft strongly recommend that all Windows users and administrators apply the latest updates immediately to mitigate the risk of exploitation. Organizations are also advised to enable automatic updates and review security policies to ensure rapid deployment of critical patches.

The discovery and patching of CVE-2025-30400 highlight the ongoing challenge of securing complex operating system components like Windows DWM.

With attackers actively exploiting such vulnerabilities to gain SYSTEM privileges, timely patching and vigilant security practices remain essential for protecting Windows environments from sophisticated threats.

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