CVE-2026-21510
Published: 10 February 2026
Summary
CVE-2026-21510 is a high-severity Protection Mechanism Failure (CWE-693) vulnerability in Microsoft Windows 10 21H2. Its CVSS base score is 8.8 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploitation for Client Execution (T1203); ranked in the top 11.4% of CVEs by exploit likelihood; CISA has added it to the Known Exploited Vulnerabilities catalog.
The strongest mitigations our analysis identified are NIST 800-53 SI-2 (Flaw Remediation) and SI-3 (Malicious Code Protection).
Threat & Defense at a Glance
Threat & Defense Details
Mitigating Controls (NIST 800-53 r5)AI
Directly addresses the protection mechanism failure by requiring identification, reporting, and timely patching of flaws like CVE-2026-21510 as detailed in Microsoft's update guide.
Mitigates exploitation of the Windows Shell bypass by deploying malicious code protection mechanisms to prevent and detect execution of attacker payloads delivered via malicious links or files.
Enables detection of systems vulnerable to CVE-2026-21510 through periodic vulnerability scanning, facilitating prioritization for remediation given its presence in CISA's KEV catalog.
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
CVE-2026-21510 is a Windows Shell protection bypass exploited remotely with user interaction (malicious link/file), enabling arbitrary code execution, directly facilitating T1203 Exploitation for Client Execution.
NVD Description
Protection mechanism failure in Windows Shell allows an unauthorized attacker to bypass a security feature over a network.
Deeper analysisAI
CVE-2026-21510 is a protection mechanism failure (CWE-693) in the Windows Shell, enabling an unauthorized attacker to bypass a security feature over a network. This vulnerability affects the Windows Shell component within Microsoft Windows operating systems. It carries a CVSS v3.1 base score of 8.8 (AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H), indicating high severity due to its network accessibility, low attack complexity, lack of privilege requirements, and potential for significant impacts on confidentiality, integrity, and availability.
The attack scenario involves a remote, unauthenticated attacker who can exploit the flaw over the network, though it requires user interaction such as clicking a malicious link or opening a file. Upon successful exploitation, the attacker can bypass Windows Shell security protections, potentially leading to arbitrary code execution, data theft, system modification, or denial of service with high impact.
Microsoft's update guide at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21510 details available patches and mitigation steps for affected systems. The vulnerability appears in CISA's Known Exploited Vulnerabilities catalog at https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-21510, signaling real-world exploitation and urging federal agencies to apply mitigations promptly.
Details
- CWE(s)
- KEV Date Added
- 10 February 2026