CVE-2026-62746 Overview
CVE-2026-62746 is a buffer over-read vulnerability in the Windows Win32K component. An authorized local attacker can read memory beyond the intended buffer boundary, resulting in information disclosure. The flaw is tracked under [CWE-126] (Buffer Over-read) and affects the kernel-mode graphics subsystem that handles user interface and window management operations.
The issue requires local access and low privileges, but no user interaction. Exploitation impacts confidentiality only. Attackers can leverage disclosed kernel memory contents to defeat address space layout randomization (ASLR) or chain the leak with other flaws for privilege escalation.
Critical Impact
A local, authenticated attacker can read out-of-bounds kernel memory in Win32K, exposing sensitive data that may include pointers, tokens, or other kernel structures useful for follow-on exploitation.
Affected Products
- Microsoft Windows 10 (versions 1607, 1809, 21H2, 22H2)
- Microsoft Windows 11 (versions 23H2, 24H2, 25H2, 26H1)
- Microsoft Windows Server 2012, 2012 R2, 2016, 2019, 2022, and 2025
Discovery Timeline
- 2026-08-11 - CVE-2026-62746 published to NVD
- 2026-08-13 - Last updated in NVD database
Technical Details for CVE-2026-62746
Vulnerability Analysis
The vulnerability resides in Win32K, the kernel-mode driver responsible for the Windows graphical subsystem, window messaging, and GDI operations. Win32K exposes a large syscall surface reachable from unprivileged user-mode processes, which historically has made it a frequent target for local attackers.
A buffer over-read occurs when code reads past the end of an allocated buffer. In this case, Win32K reads more bytes than the source object contains and returns the excess data to the caller. Because Win32K runs in kernel context, the leaked bytes come from adjacent kernel memory. That memory may contain pointers, handles, tokens, or fragments of other objects.
The vulnerability affects confidentiality only. It does not directly grant code execution or integrity impact, but leaked kernel addresses defeat ASLR and enable reliable exploitation of memory-corruption bugs.
Root Cause
The root cause is missing or incorrect length validation on a buffer accessed by Win32K, classified as [CWE-126]. The component uses a size value that exceeds the actual bounds of the allocated region, causing the read to spill into adjacent memory. Microsoft has not published the specific function or code path.
Attack Vector
Exploitation requires local, authenticated access with low privileges. An attacker runs a crafted process on the target that invokes the vulnerable Win32K syscall or graphics API with parameters that trigger the over-read. The kernel returns memory contents to the user-mode caller, which the attacker collects and analyzes offline. No user interaction is required, and the attack scope is unchanged.
Technical details on the specific syscall and parameters have not been publicly disclosed. See the Microsoft Security Update CVE-2026-62746 advisory for vendor guidance.
Detection Methods for CVE-2026-62746
Indicators of Compromise
- No public indicators of compromise have been published for CVE-2026-62746.
- No known exploitation in the wild; the CVE is not listed on the CISA Known Exploited Vulnerabilities catalog.
- The EPSS probability is 0.397%, indicating a low near-term likelihood of exploitation activity.
Detection Strategies
- Monitor endpoints for unsigned or newly introduced processes issuing unusual volumes of Win32K graphics or window-management syscalls.
- Alert on user-mode processes that repeatedly invoke NtUserCall* or GDI APIs with malformed size parameters, which can indicate over-read probing.
- Correlate local logon events with subsequent process behavior consistent with kernel information-disclosure staging, such as loading debug or memory-inspection tooling.
Monitoring Recommendations
- Enable kernel-mode audit logging where available and forward events to a centralized analytics pipeline for behavioral review.
- Track Windows Update patch state across endpoints and servers to identify unpatched hosts exposed to CVE-2026-62746.
- Baseline normal Win32K syscall patterns per host so anomalous kernel-API usage can be flagged for review.
How to Mitigate CVE-2026-62746
Immediate Actions Required
- Apply the Microsoft security update for CVE-2026-62746 to all affected Windows client and Windows Server systems.
- Prioritize multi-user systems, remote desktop hosts, and jump servers where local low-privileged accounts are common.
- Restrict local logon rights and remove interactive access for accounts that do not require it.
- Audit installed software for applications that grant untrusted users the ability to execute arbitrary code locally.
Patch Information
Microsoft has released fixes through its standard Update Guide. Refer to the Microsoft Security Update CVE-2026-62746 advisory for the KB article and specific build numbers for each affected Windows and Windows Server version. Install the update through Windows Update, Windows Server Update Services (WSUS), or your enterprise patch management platform.
Workarounds
- No official workaround has been published by Microsoft; patching is the supported remediation.
- Reduce risk by limiting local and interactive logon rights via Group Policy on high-value systems.
- Enforce application allowlisting with Windows Defender Application Control or AppLocker to block untrusted binaries from executing on affected hosts.
# Example: verify installed KB and Windows build after patching
Get-HotFix | Sort-Object -Property InstalledOn -Descending | Select-Object -First 10
[System.Environment]::OSVersion.Version
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
