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Windows Shell CVE-2026-85936

| EUVDEUVD-2026-99634 HIGH
Heap-based Buffer Overflow (CWE-122)
2026-10-13 secure@microsoft.com GHSA-p38w-2494-rxrr
8.8
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
    Deliver crafted Shell content via phishing
  2. Delivery
    User opens malicious file/link
  3. Exploit
    Trigger double-free in Windows Shell
  4. Execution
    Corrupt heap and execute code
  5. Impact
    Full compromise of user context

Vulnerability Assessment

Weakness
CWE
ASVS 5.0
V15 - Secure Coding and Architecture Heap buffer bounds checking
MITRE ATT&CK

1 technique across 1 tactic: Execution

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 be unauthenticated (PR:N) and reach the victim over a network (AV:N), but is gated by mandatory user interaction (UI:R): a user must open or interact with attacker-supplied Shell content (a crafted file, link, or shell item) for the double-free to trigger. There is no scope change (S:U), so impact is confined to the context of the interacting user rather than the system. The limiting factors are the required user action and the fact that CISA assesses the attack as not automatable, meaning it suits targeted social-engineering delivery rather than unattended mass exploitation; no special non-default configuration is indicated by the available data.

Impact

This is a genuine priority despite no confirmed exploitation. The CVSS 3.1 vector (AV:N/AC:L/PR:N/UI:R) describes a network-reachable, low-complexity, unauthenticated flaw whose only barrier is user interaction, and the CVSS 8.8 is driven by total compromise (C:H/I:H/A:H). The CWE-122 heap double-free yielding remote code execution is a classic memory-corruption primitive. The signals are largely consistent but weighted toward latent rather than active risk: CISA SSVC reports Exploitation 'none' and Automatable 'no', which aligns with the UI:R requirement (a victim must open or interact with crafted content, so mass-automated exploitation is unlikely). No EPSS score was supplied, and the CVE is NOT in CISA KEV and has no POC indicator, so this is 'no public exploit identified at time of analysis'. The one point to verify: SSVC 'Technical Impact: total' corroborates the C:H/I:H/A:H rating, so there is no conflict there. Net: a high-value target for exploit development (Windows Shell is ubiquitous) that is currently unexploited - patch promptly, but the UI:R requirement and lack of automatability place it below truly wormable network RCEs.

Exploit ScenarioDerived

An attacker crafts a malicious file, link, or shell item and lures a user into opening or interacting with it (e.g., via phishing or a malicious share), triggering a double-free in Windows Shell that corrupts the heap and leads to arbitrary code execution in the victim's context. No authentication is required of the attacker (PR:N), but successful exploitation depends on user interaction (UI:R). No public exploit code is identified at time of analysis.

This Week Schedule remediation this week. Why: HIGH severity (CVSS 7.0-8.9).
Patch available 0.6% exploitation probability (EPSS)

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AnalysisAIv1 – Oct 13, 2026

Heap corruption in the Microsoft Windows Shell allows an unauthenticated remote attacker to execute arbitrary code in the context of a user who opens or interacts with attacker-supplied Shell content, such as a crafted file, link, or shell item. Rated CVSS 8.8 (AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H), the flaw is gated by mandatory user interaction and CISA's SSVC assessment records exploitation as 'none' and the attack as not automatable, so it is best suited to targeted social-engineering delivery rather than unattended mass exploitation; no public exploit identified at time of analysis. The affected build range is broad, covering Windows 10, Windows 11 23H2 through 26H1/26H2, and Windows Server 2012 through 2025.

RemediationAI

Vendor-released patch: Microsoft has published a security update (patch status: available from vendor) and every affected branch has a fixed build threshold - apply the update that raises the system to at least 10.0.17763.9376 (Windows 10 1809 / Server 2019), 10.0.19044.7807 (Windows 10 21H2/22H2), 10.0.14393.9612 (Windows 10 1607 / Server 2016), 10.0.22631.7652 (Windows 11 23H2), 10.0.26100.9711 / 10.0.26100.33650 (Windows 11 24H2 / Server 2025), 10.0.26200.9711 (Windows 11 25H2), 10.0.28000.3231 (Windows 11 26H1), 10.0.26300.9711 (Windows 11 26H2), 6.2.9200.26434 (Server 2012), 6.3.9600.23470 (Server 2012 R2), or 10.0.20348.5761 (Server 2022), per the Microsoft MSRC advisory at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-85936. Because exploitation is gated by UI:R and the attack is assessed as not automatable, prioritizing the patch on user-facing endpoints (Windows 10/11) and on any Server installation where interactive sessions or Shell parsing of untrusted files occur is the most efficient path; Servers without interactive Shell use of untrusted content are lower urgency but should still be patched in the normal cycle. Until patching completes, compensating controls that reduce the interaction surface include disabling the Explorer preview pane and thumbnail generation for untrusted locations (Group Policy 'Turn off caching of thumbnail pictures' and related Explorer policies), which removes a common trigger path at the cost of reduced file-browsing convenience; enforcing Mark-of-the-Web / Attachment Manager policies so content downloaded from the internet cannot be opened without a prompt, which adds friction for legitimate users; and restricting or blocking untrusted file types at email and web gateways, which only mitigates one delivery vector (email/web downloads) and not file shares or removable media. Application control or WDAC/AppLocker rules limiting which binaries can launch Shell-hosted handlers reduce the attack surface further but require careful allow-listing to avoid breaking legitimate shell extensions.

Affected VersionsENISA

Windows Server 2019 (Server Core installation) 10.0.17763.0 <10.0.17763.9376
Windows 10 Version 1809 10.0.17763.0 <10.0.17763.9376
Windows 11 Version 26H2 10.0.26300.0 <10.0.26300.9711
Windows Server 2025 (Server Core installation) 10.0.26100.0 <10.0.26100.33650
Windows Server 2012 R2 6.3.9600.0 <6.3.9600.23470
Windows 11 Version 23H2 10.0.22631.0 <10.0.22631.7652
Windows Server 2022 10.0.20348.0 <10.0.20348.5761
Windows Server 2019 10.0.17763.0 <10.0.17763.9376
Windows Server 2016 10.0.14393.0 <10.0.14393.9612
Windows 11 Version 24H2 10.0.26100.0 <10.0.26100.9711
Windows 11 Version 25H2 10.0.26200.0 <10.0.26200.9711
Windows Server 2012 (Server Core installation) 6.2.9200.0 <6.2.9200.26434
Windows Server 2016 (Server Core installation) 10.0.14393.0 <10.0.14393.9612
Windows 11 version 26H1 10.0.28000.0 <10.0.28000.3231
Windows Server 2012 R2 (Server Core installation) 6.3.9600.0 <6.3.9600.23470
Windows Server 2012 6.2.9200.0 <6.2.9200.26434
Windows 10 Version 22H2 10.0.19045.0 <10.0.19044.7807
Windows 10 Version 21H2 10.0.19044.0 <10.0.19044.7807
Windows 10 Version 1607 10.0.14393.0 <10.0.14393.9612
Windows Server 2025 10.0.26100.0 <10.0.26100.33650

Affected Packages

euvd windows_10_version_1607 fix: 10.0.14393.9612
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_2012 fix: 6.2.9200.26434
euvd windows_server_2012_r2 fix: 6.3.9600.23470
euvd windows_server_2012_r2_server_core_installation fix: 6.3.9600.23470
euvd windows_server_2012_server_core_installation fix: 6.2.9200.26434
euvd windows_server_2016 fix: 10.0.14393.9612
euvd windows_server_2016_server_core_installation fix: 10.0.14393.9612
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 20 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 Shell (explorer.exe and the shell32/SHLWAPI component family, including thumbnail, icon, and shell-item handlers) is the component that parses and renders files, shortcuts, and namespace objects presented to the user. The defect is a heap memory-management error in that parsing path: the advisory describes a double free, while the assigned weakness class is CWE-122 (heap-based buffer overflow) and the source tags 'Buffer Overflow' and 'Heap Overflow' - all of these point to the same practical failure mode, memory being released or written outside its allocated boundaries during Shell handling of attacker-influenced content. The consequence is heap corruption that can be shaped into controlled memory writes and, ultimately, code execution in the security context of the interacting user. Because the CVSS vector keeps scope unchanged (S:U), the impact is confined to that user's context rather than escalating to a system-wide compromise, although a user with administrative rights would still yield a high-privilege foothold. The network attack vector (AV:N) with no privileges required (PR:N) reflects that the malicious content is delivered remotely, while the mandatory user interaction (UI:R) is the compensating control that limits automation.

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  • Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

Vendor (microsoft) PRIMARY 8.8 HIGH
AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
vuln.today AI 8.8 HIGH

Network-reachable unauthenticated double-free (AV:N/PR:N) gated by required user interaction (UI:R); heap RCE in user context gives total C/I/A with no scope change.

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

Primary rating from Vendor (microsoft).

CVSS VectorVendor: microsoft

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
Required
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 8.8

DescriptionCVE.org

Double free in Windows Shell allows an unauthorized attacker to execute code over a network.

Executive ViewAI

Why It Matters

A heap corruption flaw in the Microsoft Windows Shell (CVE-2026-85936) lets an attacker execute arbitrary code with the full privileges of any user who opens or interacts with crafted Shell content, which means ordinary day-to-day file and link handling is the delivery path. Because the flaw spans Windows 10, Windows 11 23H2 through 26H2, and Windows Server 2012 through 2025, essentially the entire Windows estate is in scope, and successful exploitation would give an attacker the user's access to data, credentials, and connected systems. The good news is that exploitation requires a user to open the malicious content, no public exploit has been identified at the time of analysis, and a vendor patch is available, so this is a manageable, high-priority remediation rather than an active incident.

Business Impact: High
Compensating Controls

Apply vendor patch.

Threat Intelligence Overview

EPSS Score
0.6%
Top 55% exploitable
Prevalence
Ubiquitous
Windows Shell is a core component of every supported Windows release
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 0.6%
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
Scheduled
Exploitation
None
System Exposure· derived
Open
Automatable
No
Human Impact
High
Technical Impact
Total

Priority Score

45
Low Medium High Critical
KEV: 0
EPSS: +1
CVSS: +44
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

A buffer overflow occurs when a program writes more data to a memory buffer than it was allocated to hold, causing the excess data to spill into adjacent memory regions.

A heap overflow occurs when a program writes data beyond the bounds of a buffer allocated in the heap memory region.

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