Zero-day vulnerability in Windows

Protection Mechanism Failure
CVE-2026-21510

Vulnerability details

Advisory: SB2026021055 - Security feature bypass vulnerability in Windows Shell

Vulnerable component: Windows

CVE-ID: CVE-2026-21510

CVSSv3 score: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H/E:H/RL:O/RC:C

CWE-ID: CWE-693 - Protection Mechanism Failure

Description:

The vulnerability allows a remote attacker to bypass implemented security restrictions.

The vulnerability exists due to insufficient implementation of security measures. An attacker can trick the victim into clicking on a specially crafted URL or shortcut file to bypass Windows SmartScreen and Windows Shell security prompts and execute arbitrary code on the system.

Note, the vulnerability is being actively exploited in the wild.

External links:

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21510

About zero-day vulnerabilities

Zero-day vulnerability is an undisclosed vulnerability in software that hackers can exploit to compromise computer programs, gain unauthorized access to sensitive data, penetrate networks, etc. We consider vulnerability a zero-day when there is no solution provided from software vendor and the vulnerability is being actively exploited by malicious actors.

Zero-day candidate is a potential zero-day vulnerability in software which might have been used in targeted attacks, however there is no evidence to support this suggestion.