CVE-2025-27728 Overview
CVE-2025-27728 is an out-of-bounds read vulnerability in Windows Kernel-Mode Drivers. An authenticated local attacker can exploit the flaw to elevate privileges on affected systems. Microsoft published the advisory on April 8, 2025, and assigned a CVSS 3.1 base score of 7.8. The weakness is tracked under [CWE-125] (Out-of-bounds Read) and affects modern Windows client and server platforms, including Windows 11 24H2 and Windows Server 2025. Successful exploitation gives an attacker the ability to compromise confidentiality, integrity, and availability at the kernel level.
Critical Impact
A local, authenticated attacker who exploits this out-of-bounds read in a Windows kernel-mode driver can escalate to SYSTEM-level privileges, undermining OS-enforced security boundaries.
Affected Products
- Microsoft Windows 11 version 24H2
- Microsoft Windows Server 2025
- Systems running vulnerable Windows Kernel-Mode Drivers prior to the April 2025 security update
Discovery Timeline
- 2025-04-08 - CVE-2025-27728 published to NVD and addressed in Microsoft's April 2025 security update
- 2026-06-17 - Last updated in NVD database
Technical Details for CVE-2025-27728
Vulnerability Analysis
The vulnerability resides in a Windows Kernel-Mode Driver that reads data beyond the bounds of an allocated buffer. Kernel-mode drivers execute at Ring 0, so a memory-safety defect in this layer bypasses standard user-mode protections. An authorized local user can trigger the driver code path with crafted input and cause the kernel to read memory outside the intended object. The out-of-bounds data may contain kernel pointers, credentials, or object references that an attacker uses to construct a full privilege escalation primitive. Chained with other primitives, this class of flaw commonly enables tampering with process tokens to obtain SYSTEM.
Root Cause
The defect is classified as [CWE-125], an out-of-bounds read caused by missing or incorrect validation of buffer offsets or length fields. When the driver processes attacker-controlled input, it reads past the end of a memory region without verifying that the read remains within bounds. The result is leakage of adjacent kernel memory contents into a location the caller can observe.
Attack Vector
The CVSS vector indicates a local attack path requiring low privileges and no user interaction. An attacker must already have code execution as a standard user, typically obtained through phishing, a browser exploit, or an existing foothold. The attacker then interacts with the vulnerable driver, usually by issuing IOCTLs or system calls that reach the flawed code path. Because no verified public exploit or proof-of-concept has been published, exploitation currently requires independent reverse engineering of the patched driver.
No verified public exploit code is available. Microsoft has not disclosed the specific driver or IOCTL involved. See the Microsoft Security Update CVE-2025-27728 advisory for vendor guidance.
Detection Methods for CVE-2025-27728
Indicators of Compromise
- Unexpected SYSTEM tokens on processes launched by standard user accounts
- Kernel bug checks or driver-related crash dumps immediately following user-mode activity from non-administrative processes
- Loading of unusual kernel drivers or execution of unsigned tooling from user-writable paths such as %TEMP% or %APPDATA%
Detection Strategies
- Enable Windows kernel auditing and monitor for anomalous IOCTL patterns against kernel-mode drivers
- Track token manipulation and parent-child process anomalies where a low-privilege process spawns a SYSTEM child
- Correlate Event ID 4672 (special privileges assigned) with process lineage that lacks administrative ancestry
Monitoring Recommendations
- Ingest endpoint telemetry, Sysmon, and Windows Security logs into a centralized data lake for behavioral correlation
- Baseline normal driver load and IOCTL behavior per host, then alert on deviations
- Prioritize alerts on hosts that missed the April 2025 or later Windows cumulative update
How to Mitigate CVE-2025-27728
Immediate Actions Required
- Apply the April 2025 Microsoft security update to all Windows 11 24H2 and Windows Server 2025 systems
- Inventory endpoints and servers to confirm patch deployment status across the fleet
- Restrict local logon and interactive access on high-value servers to reduce the pool of accounts able to exploit local flaws
- Enforce application allowlisting to prevent unauthorized binaries from reaching vulnerable driver interfaces
Patch Information
Microsoft released a fix through the April 2025 Patch Tuesday cycle. Refer to the Microsoft Security Update CVE-2025-27728 advisory for the specific KB articles and build numbers applicable to Windows 11 24H2 and Windows Server 2025. Apply the update through Windows Update, WSUS, Microsoft Update Catalog, or your patch management platform.
Workarounds
- No official workaround is documented by Microsoft; patching is the required remediation
- Reduce exposure by removing unnecessary local user accounts and enforcing least privilege
- Enable Attack Surface Reduction rules and Hypervisor-Protected Code Integrity (HVCI) to raise the cost of kernel exploitation
# Verify patch installation status on Windows via PowerShell
Get-HotFix | Sort-Object -Property InstalledOn -Descending | Select-Object -First 10
# Confirm current OS build (compare against fixed builds listed in the MSRC advisory)
[System.Environment]::OSVersion.Version
(Get-ItemProperty 'HKLM:\SOFTWARE\Microsoft\Windows NT\CurrentVersion').CurrentBuild
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
