Windows
CVE-2026-21510
HIGH
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
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Lifecycle Timeline
4DescriptionCVE.org
Protection mechanism failure in Windows Shell allows an unauthorized attacker to bypass a security feature over a network.
Articles & Coverage 1
AnalysisAI
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.
Technical ContextAI
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.
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.
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External POC / Exploit Code
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