Windows
CVE-2026-21510
HIGH
Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain
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AccessCraft malicious network packet
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ExploitTrigger Shell protection bypass
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ImpactExecute arbitrary code with user privileges
Vulnerability Assessment
| Weakness |
CWE
OWASP Top 10:2025
A06:2025 - Insecure Design
ASVS 5.0
V15 - Secure Coding and Architecture Protection mechanism completeness
|
| Exploitation Conditions | Windows Shell with default security protections enabled. Requires user interaction (UI:R) to click malicious content or accept network-delivered payload. Remote unauthenticated exploitation against vulnerable Windows systems on network-accessible hosts. |
| Impact | CVSS 8.8 (High). KEV-listed — actively exploited. EPSS 3.8%. No authentication required. Remote exploitation over network. Bypasses fundamental Windows security features (MOTW, SmartScreen). High value for phishing and drive-by attacks. |
| Exploit ScenarioDerived | An attacker delivers a crafted file (via email attachment, download link, or network share) that exploits the Shell bypass to avoid triggering Windows security features. The file appears safe to both Windows and the user — no SmartScreen warning, no Protected View, no MOTW prompt. When opened, the malicious payload executes with the user's full privileges, enabling malware installation, credential theft, or further exploitation. |
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Alert meAnalysisAIv1 – Mar 12, 2026
Windows Shell contains a protection mechanism failure (CVE-2026-21510, CVSS 8.8) that allows unauthenticated remote attackers to bypass security features over a network. KEV-listed, this vulnerability in the core Windows Shell component enables remote code execution by circumventing security boundaries designed to prevent execution of untrusted content received from the network.
Earlier versions of this analysis (1)
Windows Shell contains a protection mechanism failure (CWE-693) that allows remote attackers to bypass security features designed to prevent execution of malicious content received over the network.
RemediationAI
Apply Microsoft security update immediately. Enable ASR rules for additional Office and Shell protections. Monitor for files bypassing MOTW indicators. Implement email gateway filtering for suspicious attachments.
Affected Packages
Source: OSV (Open Source Vulnerabilities)
Affects your stack
Affects 15 packages in microsoft
Checking this CVE against your own stacks and servers is part of the Basic plan and up.
Technical ContextAI · show details
Windows Shell handles file associations, shortcut resolution, and rendering of downloaded content. Security mechanisms like Mark of the Web (MOTW), SmartScreen, and Protected View rely on Shell correctly identifying untrusted content. This vulnerability allows attackers to craft content that bypasses these protections, enabling execution of malicious payloads without the security warnings that users expect.
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- Exploit and PoC references, threat intelligence from 22 sources
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Severity by source
AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Primary rating from NVD · only source for this CVE.
CVSS VectorNVD
Lifecycle Timeline
3DescriptionCVE.org
Protection mechanism failure in Windows Shell allows an unauthorized attacker to bypass a security feature over a network.
Articles & Coverage 1
Executive ViewAI
CVE-2026-21510 is a critical Windows Shell vulnerability actively exploited in the wild that allows attackers to bypass security controls and gain unauthorized network access to affected systems. This poses an immediate threat to any organization running vulnerable Windows environments, potentially enabling attackers to compromise systems without a patch currently available.
Implement network segmentation to restrict shell protocol access; deploy Web Application Firewall (WAF) rules to block malicious Shell requests; disable Windows Shell features and services where business operations permit; enforce strict network access controls and firewall policies limiting Shell-based communications; deploy behavioral analysis and anomaly detection through EDR/XDR solutions; implement application whitelisting to prevent unauthorized Shell execution; increase monitoring and logging of Shell-related activities; enforce multi-factor authentication on critical systems; isolate high-value assets from general network access.
Threat Intelligence Overview
NVD
CVE.org
CISA KEV
EPSS
GitHub
VulDB
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.
What every action level means
SSVC AssessmentENISA
Priority Score
Affected Products (CPE)CVE.org
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Exploit-DB