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CVE-2026-65788 is a use-after-free (UAF) vulnerability in Microsoft’s Desktop Window Manager (DWM) that allows an authenticated local attacker to elevate privileges to SYSTEM level. The vulnerability resides in the `dwmcore.dll` component, specifically within the destructor of the `CSynchronousSuperWetInk` class. DWM is the Windows compositing window manager responsible for rendering all graphical elements on the display, making it a high-value target for privilege escalation attacks.
The root cause lies in a logic error within the `CSynchronousSuperWetInk::~CSynchronousSuperWetInk` destructor. When this destructor executes, it conditionally removes the object from the CSuperWetInkManager‘s internal vector based on the return value of IsSuperWetCompatible(). Under specific conditions, the conditional check fails to properly clean up the dangling pointer, allowing it to persist in the manager’s vector after the object has been freed. This creates a use-after-free condition where a subsequent operation can reference the already-freed memory region.
An attacker with low-privileged local access can trigger this UAF by crafting specific inputs or operations that interact with the DWM’s ink rendering functionality. The attack complexity is rated HIGH due to the need for race conditions or specific timing to reliably exploit the dangling pointer. Successful exploitation provides the attacker with the ability to execute arbitrary code in the context of the DWM process, which runs with SYSTEM privileges, effectively allowing a local user to gain full control over the compromised system.
Patch diffing analysis between the vulnerable and patched versions of `dwmcore.dll` reveals that the fix addresses the conditional logic in the destructor, ensuring proper removal of the object from the manager’s vector. The vulnerability affects multiple Windows 11 versions including 23H2, 24H2, 25H2, and 26H1, as well as Windows Server 2025. Microsoft released a security update addressing this vulnerability as part of the August 2026 Patch Tuesday.
DailyCVE Form:
Platform: Windows 11 23H2/24H2/25H2/26H1, Server 2025
Version: 10.0.22631.7517 (23H2), 10.0.26100.9106 (24H2), 10.0.26200.9106 (25H2), <10.0.28000.2704 (26H1)
Vulnerability: Use-After-Free in DWM
Severity: HIGH (CVSS 3.1: 7.0)
Date: August 11, 2026
Prediction: Patch already available (August 2026)
What Undercode Say:
Analytics from Elastic Security Labs’ patch diff analysis reveals the following key findings:
BSim Patch Diff Report between vulnerable and patched dwmcore.dll:
</h1>
<h1>BSIM PATCH DIFF REPORT</h1>
File 1: dwmcore_vuln.dll
<h1>File 2: dwmcore_patched.dll</h1>
TOP 10 MOST MODIFIED FUNCTIONS
dwmcore_vuln.dll dwmcore_patched.dll Sim Jaccard
FUN_1802e7842 FUN_1802e7842 0.1191 0.0632
FUN_1802e92d6 FUN_1802e92d6 0.1470 0.0722
FUN_1802e5faa FUN_1802e5faa 0.1741 0.0769
~CDelegatedInkCanvas ~CDelegatedInkCanvas 0.7556 0.6047
GetBufferedOutputTransformed GetBufferedOutputTransformed 0.7628 0.6154
FrameStarted FrameStarted 0.7833 0.6429
~CSynchronousSuperWetInk ~CSynchronousSuperWetInk 0.8018 0.6667
FUN_1802f5aa2 FUN_1802f5aa2 0.9127 0.8393
<h1>FUN_1802f57d2 FUN_1802f5d72 0.9127 0.8393</h1>
The `~CSynchronousSuperWetInk` destructor shows significant changes between versions, confirming this is the patched function.
Exploit: (Educational Purposes!)
The exploitation flow follows these conceptual steps:
- Spray the heap with controlled objects to achieve predictable memory layout
- Trigger the UAF by invoking the vulnerable `CSynchronousSuperWetInk` destructor path, leaving a dangling pointer in `CSuperWetInkManager`
3. Reclaim the freed memory with attacker-controlled data using heap spraying techniques - Invoke the dangling pointer through `DirtyActiveInk` iteration, causing a controlled vtable call
- Redirect execution to attacker-controlled shellcode to spawn a SYSTEM shell
The vulnerability provides reliable privilege escalation from low-privileged user to SYSTEM. The exploit uses the dangling pointer’s RCX register pointing to sprayed objects to deliver controlled vtable calls.
Protection:
- Install the Microsoft security update addressing CVE-2026-65788 (August 2026 Patch Tuesday)
- Update to the following fixed versions:
- Windows 11 23H2: 10.0.22631.7517 or later
- Windows 11 24H2: 10.0.26100.9106 or later
- Windows 11 25H2: 10.0.26200.9106 or later
- Windows 11 26H1: 10.0.28000.2704 or later
- Apply the patch via Windows Update or Microsoft Update Catalog
- Restrict local access to trusted users only
- Enable Windows Defender and exploit protection features
Impact:
Successful exploitation allows a local authenticated attacker to elevate privileges to SYSTEM level, gaining complete control over the affected system. The attacker can read all data, modify or delete any files, and compromise the availability of the system. The vulnerability requires local access and has HIGH attack complexity, but requires no user interaction. EPSS score is 1.4% (70th percentile), indicating moderate likelihood of exploitation. The vulnerability affects all major Windows 11 versions and Windows Server 2025.
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Sources:
Reported By: nvd.nist.gov
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