CVE-2026-21510
Published: February 10, 2026
Official Description
Microsoft Windows Shell contains a protection mechanism failure vulnerability that could allow an unauthorized attacker to bypass a security feature over a network.
CISA KEV Advisory
Microsoft Windows Shell Protection Mechanism Failure Vulnerability
Microsoft Windows Shell contains a protection mechanism failure vulnerability that could allow an unauthorized attacker to bypass a security feature over a network.
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
Risk Analysis
This high-severity vulnerability in Microsoft Windows Shell allows an unauthenticated remote attacker to bypass a security feature. With a CVSS score of 8.8, it poses a significant risk. Despite a low EPSS score of 0.02720, its inclusion in CISA's KEV catalog indicates confirmed exploitation.
This vulnerability is being actively exploited in the wild and is listed in CISA's KEV catalog. It is remotely exploitable, requiring user interaction to bypass the security feature.
Install the latest security patches from Microsoft for Windows Shell. Implement network segmentation and user awareness training to reduce the risk of remote attacks.
Technical Analysis
CVE-2026-21510 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.
Exploitation does not require any privileges, though user interaction (Required) is needed, which slightly reduces the risk of mass automated attacks.
A successful exploit results in complete confidentiality breach (data exposure), full integrity compromise (data manipulation), availability disruption (denial of service), with a CVSS base score of 8.8.
CISA has added CVE-2026-21510 to the Known Exploited Vulnerabilities (KEV) catalog, confirming active exploitation in the wild. U.S. federal agencies are required to patch this within the mandated timeframe, and all organizations should treat remediation as urgent.
CVSS v3.1 Vector Breakdown
Affected Vendors & Products
Exploit & PoC Resources
News & Research Mentioning CVE-2026-21510
CISA has added six new vulnerabilities to its Known Exploited Vulnerabilities (KEV) Catalog, based on evidence of active exploitation. CVE-2026-21510 Microsoft Windows Shell Protection Mechanism Failure Vulnerability CVE-2026-21513 Microsoft MSHTML Framework Security Feature Bypass Vulnerability CVE-2026-21514 Microsoft Office Word Reliance on Untrusted Inputs in a Security Decision Vulnerability CVE-2026-21519 Microsoft Windows Type Confusion Vulnerability CVE-2026-21525 Microsoft Windows NULL Pointer Dereference Vulnerability CVE-2026-21533 Windows Remote Desktop Services Elevation of Privilege Vulnerability These types of vulnerabilities are frequent attack vectors for malicious cyber actors and pose significant risks to the federal enterprise. Bi [xlite_meta score:53 src:CISA Alerts xlite_fp:88d5ff4976309c17f8264912552cef85549f24eb7de38b00c6011d2454de9f37]
All References (2)
Quick Facts
Known Threat Actors
Recommended Actions
- →Apply vendor patches immediately
- →Monitor CVE-2026-21510 in threat intel feeds
- →Review IDS/IPS signatures for exploitation attempts
- !CISA KEV: Federal agencies must patch per BOD 22-01 timeline
- !Active exploitation confirmed — treat as P1