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CVE-2026-21510

Microsoft Windows Shell Protection Mechanism Failure

8.8 HIGHActively exploited (CISA KEV)EPSS 24.5%
  1. Published10 Feb 2026
  2. Added to CISA KEV10 Feb 2026
  3. Remediation due3 Mar 2026
Actively exploited (CISA KEV)

Microsoft Windows Shell contains a protection mechanism failure vulnerability that could allow an unauthorized attacker to bypass a security feature over a network.

Added to KEV: 10 Feb 2026Federal remediation due: 3 Mar 2026

Description

Protection mechanism failure in Windows Shell allows an unauthorized attacker to bypass a security feature over a network.

CVSS 3.1 breakdown

Attack vectorNetwork
Attack complexityLow
Privileges requiredNone
User interactionRequired
ScopeUnchanged
ConfidentialityHigh
IntegrityHigh
AvailabilityHigh
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

Affected products

Microsoft Windows 10 1607< 10.0.14393.8868
Microsoft Windows 10 1809< 10.0.17763.8389
Microsoft Windows 10 21h2< 10.0.19044.6937
Microsoft Windows 10 22h2< 10.0.19045.6937
Microsoft Windows 11 23h2< 10.0.22631.6649
Microsoft Windows 11 24h2< 10.0.26100.7781
Microsoft Windows 11 25h2< 10.0.26200.7781
Microsoft Windows Server 2012r2
Microsoft Windows Server 2016< 10.0.14393.8868
Microsoft Windows Server 2019< 10.0.17763.8389
Microsoft Windows Server 2022< 10.0.20348.4711
Microsoft Windows Server 2022 23h2< 10.0.25398.2149
Microsoft Windows Server 2025< 10.0.26100.32313

Remediation

Fixed in
Microsoft Windows 10 1607≥ 10.0.14393.8868
Microsoft Windows 10 1809≥ 10.0.17763.8389
Microsoft Windows 10 21h2≥ 10.0.19044.6937
Microsoft Windows 10 22h2≥ 10.0.19045.6937
Microsoft Windows 11 23h2≥ 10.0.22631.6649
Microsoft Windows 11 24h2≥ 10.0.26100.7781
Microsoft Windows 11 25h2≥ 10.0.26200.7781
Microsoft Windows Server 2016≥ 10.0.14393.8868
Microsoft Windows Server 2019≥ 10.0.17763.8389
Microsoft Windows Server 2022≥ 10.0.20348.4711

References

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Frequently asked

Is CVE-2026-21510 being actively exploited?

Yes. CVE-2026-21510 is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, added 10 Feb 2026.

How severe is CVE-2026-21510?

CVE-2026-21510 has a CVSS 3.1 base score of 8.8, rated high. EPSS estimates a 24.5% probability of exploitation.

Which products are affected by CVE-2026-21510?

Affected products include Microsoft Windows 10 1607, Microsoft Windows 10 1809, Microsoft Windows 10 21h2, Microsoft Windows 10 22h2, Microsoft Windows 11 23h2, and 8 more.

How do I fix CVE-2026-21510?

Upgrade affected software to a fixed version, for example Microsoft Windows 10 1607 10.0.14393.8868, Microsoft Windows 10 1809 10.0.17763.8389, Microsoft Windows 10 21h2 10.0.19044.6937 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2026-21510 against the real software inventory on every managed device, every day. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. Because it is on the CISA KEV list, Secuno flags any affected asset as top-priority automatically. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.

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Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.