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Windows DWM CVE-2026-85854

| EUVDEUVD-2026-99558 HIGH
Use After Free (CWE-416)
2026-10-13 secure@microsoft.com GHSA-xmpm-xfj9-gpx6
7.0
CVSS 3.1 · Vendor: microsoft
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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain

  1. Access
    Obtain low-privileged local foothold
  2. Delivery
    Launch crafted process invoking DWM Core
  3. Exploit
    Trigger use-after-free race in freed object
  4. Execution
    Reclaim memory to hijack control flow
  5. Impact
    Elevate to SYSTEM privileges

Vulnerability Assessment

Weakness
CWE
ASVS 5.0
V15 - Secure Coding and Architecture Memory lifecycle management
MITRE ATT&CK

2 techniques across 2 tactics: Execution, Privilege Escalation

The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up.

Exploitation Conditions

Exploitation requires the attacker to already possess local access and low-level (non-elevated) privileges on the target host - this is a local privilege-escalation primitive (AV:L/PR:L), not remotely reachable. The use-after-free in the Windows DWM Core Library must be triggered through local interaction with the Desktop Window Manager graphics subsystem, and the high attack complexity (AC:H) indicates a race condition or precise heap/timing state the attacker must reliably win, which limits reliability and rules out trivial one-shot exploitation. No user interaction is needed (UI:N). The chief limiting factors are the pre-required local foothold and the difficult-to-win race window; the affected product is any unpatched supported Windows build below the fixed versions listed (e.g., Windows 11 24H2 <10.0.26100.9711, Server 2025 <10.0.26100.33650).

Impact

This is a genuine but moderate-priority elevation-of-privilege flaw rather than a drop-everything emergency. The CVSS 3.1 base score of 7.0 (AV:L/AC:H/PR:L/UI:N/S:U) reflects meaningful tempering factors: the attacker must already have local access and low-level privileges (PR:L) on the host, and exploitation is rated high-complexity (AC:H), implying a race condition or specific timing/heap-state window typical of use-after-free (CWE-416) bugs. Offsetting this, the impact is high across confidentiality, integrity, and availability (C:H/I:H/A:H), consistent with kernel/graphics-subsystem privilege escalation. No EPSS score, CISA KEV listing, or public POC is present in the supplied intelligence, so there is no evidence of active exploitation or weaponization - the real-world exploitation likelihood signal is currently weak. No SSVC decision data (automatable/exploitation/technical-impact) was provided. In practice this is a classic second-stage local EoP: valuable to an attacker who already has a foothold (e.g., post-phishing or post-RCE) to escalate to SYSTEM, but not remotely reachable and not trivially exploitable. Prioritize patching on multi-user, shared, or high-value hosts; it is lower urgency than a network-facing unauthenticated flaw.

Exploit ScenarioDerived

An attacker who has already gained low-privileged local code execution (for example via a phishing payload or a compromised standard user account) runs a crafted program that manipulates the Windows DWM Core Library into a use-after-free condition. By winning the required race/timing window (AC:H), they reclaim the freed object to corrupt memory and execute code at elevated privilege. No public exploit code is identified in the provided data, so a working exploit would require independent development against the race condition.

This Week Schedule remediation this week. Why: HIGH severity (CVSS 7.0-8.9).
Patch available 0.3% exploitation probability (EPSS)

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AnalysisAIv1 – Oct 13, 2026

Local privilege escalation in the Windows Desktop Window Manager (DWM) Core Library affects unpatched supported builds of Windows 10, Windows 11 (23H2 through 26H2), Windows Server 2019, Server 2022, and Server 2025, where a use-after-free in the desktop compositor lets a locally authenticated, low-privileged attacker corrupt memory and run code at a higher integrity level. Exploitation requires an existing foothold on the host (AV:L/PR:L) and is rated high complexity (AC:H), consistent with a timing- or heap-state-dependent race in the graphics subsystem that an attacker must win reliably, so this is a genuine but moderate-priority elevation-of-privilege issue rather than a drop-everything emergency. No public exploit code has been identified at time of analysis and the flaw has not been confirmed actively exploited (CISA KEV); Microsoft has released fixed builds through the MSRC update guide.

RemediationAI

Vendor-released patch: apply the Microsoft security update for CVE-2026-85854, which raises affected systems to Windows 10 21H2/22H2 build 10.0.19044.7807, Windows 10 1809 and Server 2019 build 10.0.17763.9376, Windows 11 23H2 build 10.0.22631.7652, Windows 11 24H2 and Server 2025 build 10.0.26100.9711 / 10.0.26100.33650, Windows 11 25H2 build 10.0.26200.9711, Windows 11 26H1 build 10.0.28000.3231, Windows 11 26H2 build 10.0.26300.9711, and Server 2022 build 10.0.20348.5761; deployment guidance and detection details are at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-85854. Because this is a local elevation-of-privilege primitive, the practical compensating controls are to deny or heavily audit local logon and interactive/RDP access for untrusted accounts, strip unnecessary local interactive rights and administrative group memberships so that a low-privileged foothold is harder to obtain in the first place, and enable Windows Defender Application Control or the relevant Attack Surface Reduction and memory-protection features to raise the cost of heap/use-after-free exploitation - accepting that these reduce functionality and administrative convenience and none of them remove the underlying defect. Disabling the DWM compositor is not a realistic workaround on supported Windows versions, as it degrades or breaks the desktop experience across all sessions, so patching remains the only complete fix; until the update is deployed, prioritize hosts where unprivileged local or multi-user interactive access is common, such as Remote Desktop and terminal server roles.

Affected VersionsENISA

Windows 10 Version 21H2 10.0.19044.0 <10.0.19044.7807
Windows 11 Version 25H2 10.0.26200.0 <10.0.26200.9711
Windows Server 2019 (Server Core installation) 10.0.17763.0 <10.0.17763.9376
Windows 11 Version 26H2 10.0.26300.0 <10.0.26300.9711
Windows 11 Version 24H2 10.0.26100.0 <10.0.26100.9711
Windows Server 2025 (Server Core installation) 10.0.26100.0 <10.0.26100.33650
Windows Server 2019 10.0.17763.0 <10.0.17763.9376
Windows 11 version 26H1 10.0.28000.0 <10.0.28000.3231
Windows Server 2022 10.0.20348.0 <10.0.20348.5761
Windows 11 Version 23H2 10.0.22631.0 <10.0.22631.7652
Windows Server 2025 10.0.26100.0 <10.0.26100.33650
Windows 10 Version 22H2 10.0.19045.0 <10.0.19044.7807
Windows 10 Version 1809 10.0.17763.0 <10.0.17763.9376

Affected Packages

euvd windows_10_version_1809 fix: 10.0.17763.9376
euvd windows_10_version_21h2 fix: 10.0.19044.7807
euvd windows_10_version_22h2 fix: 10.0.19044.7807
euvd windows_11_version_23h2 fix: 10.0.22631.7652
euvd windows_11_version_24h2 fix: 10.0.26100.9711
euvd windows_11_version_25h2 fix: 10.0.26200.9711
euvd windows_11_version_26h1 fix: 10.0.28000.3231
euvd windows_11_version_26h2 fix: 10.0.26300.9711
euvd windows_server_2019 fix: 10.0.17763.9376
euvd windows_server_2019_server_core_installation fix: 10.0.17763.9376
euvd windows_server_2022 fix: 10.0.20348.5761
euvd windows_server_2025 fix: 10.0.26100.33650
euvd windows_server_2025_server_core_installation fix: 10.0.26100.33650

Source: OSV (Open Source Vulnerabilities)

Affects your stack

Affects 13 packages in euvd

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

Technical ContextAI · show details

The Windows Desktop Window Manager (DWM), implemented largely in dwmcore.dll, is the compositor responsible for rendering and managing window surfaces, composition buffers, and the shared graphics state for every interactive session. This issue is a use-after-free (CWE-416): an object allocated and tracked by the DWM Core Library is released while a stale reference to it remains, and that freed memory is subsequently dereferenced or reallocated, producing memory corruption that the attacker can steer into controlled execution. The assessed vector (CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H) indicates the defect is only reachable from the local machine by a caller holding low (non-administrative) privileges, that no user interaction beyond the attacker's own local actions is required, and that the high attack complexity reflects a race window or precise heap/timing state that must be satisfied for the stale reference to be used before the allocation is reclaimed. Successful corruption yields full loss of confidentiality, integrity, and availability within the DWM process's security context, which is what converts a local foothold into an elevation of privilege. The CPE-relevant scope spans the client and server Windows servicing branches enumerated in EUVD-2026-99558, including Server Core installations where DWM still participates in session compositing.

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  • Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

Vendor (microsoft) PRIMARY 7.0 HIGH
AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
vuln.today AI 7.0 HIGH

Local use-after-free requiring an existing low-privileged account (PR:L) and a hard-to-win race (AC:H); successful escalation yields full C/I/A impact with no scope change.

3.1 AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
4.0 AV:L/AC:H/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

Primary rating from Vendor (microsoft).

CVSS VectorVendor: microsoft

Attack Vector
Local
Attack Complexity
High
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

Lifecycle Timeline

2
Patch available
Oct 13, 2026 - 20:20 EUVD
CVE Published
Oct 13, 2026 - 19:21 cve.org
HIGH 7.0

DescriptionCVE.org

Use after free in Windows DWM Core Library allows an authorized attacker to elevate privileges locally.

Executive ViewAI

Why It Matters

A high-severity local privilege escalation vulnerability in the Windows Desktop Window Manager Core Library affects supported builds of Windows 10, Windows 11 (23H2-26H2), and Windows Server 2019/2022/2025. An attacker who already has a low-privileged foothold on a host could exploit this flaw to gain higher integrity level access, potentially compromising sensitive data or expanding control over the system. No public exploit identified at time of analysis, but unpatched systems remain at risk and should be prioritized for remediation.

Business Impact: Medium
Compensating Controls

Apply vendor patch.

Threat Intelligence Overview

EPSS Score
0.3%
Top 85% exploitable
Prevalence
Ubiquitous
DWM Core is a core Windows graphics component present in all supported Windows versions
Vendor Status
Publicly Disclosed:No
Exploited:No
Latest Software Release:Exploitation Less Likely
Data Quality
5 sources
Confidence: Medium

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue
Severity HIGH
CISA KEV No
Public POC No
EPSS 0.3%
Patch available Yes
Active threat No
Deciding rule
HIGH severity (CVSS 7.0-8.9)
What every action level means
Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.
Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.
This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.
This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.
Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision
Defer
Exploitation
None
System Exposure· derived
Small
Automatable
No
Human Impact
Medium
Technical Impact
Total

Priority Score

35
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +35
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

Use-after-free vulnerabilities occur when a program continues to access memory through a pointer after that memory has been deallocated.

Memory corruption occurs when a program writes data beyond the boundaries of allocated memory regions or accesses memory in unintended ways, violating the integrity of the process's address space.

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