How severe is CVE-2026-21513?

CVE-2026-21513 has a CVSS 3.x base score of 8.8, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2026-21513 being actively exploited?

Yes. CVE-2026-21513 is on CISA's Known Exploited Vulnerabilities (KEV) catalog, added on 2026-02-10, which means active exploitation has been confirmed. It should be prioritised for remediation.

What products are affected by CVE-2026-21513?

CVE-2026-21513 primarily affects Microsoft Windows 10 1607. In total, 23 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2026-21513?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Because this CVE is known to be actively exploited, treat remediation as urgent — CISA KEV typically sets a short remediation deadline.

Does CVE-2026-21513 have an EU (EUVD) identifier?

Yes. CVE-2026-21513 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-7342. It is also flagged as exploited in the EUVD (since 2026-02-10).

When was CVE-2026-21513 published?

CVE-2026-21513 was published on 2026-02-10 and last updated on 2026-06-17.

CVE-2026-21513

CVE-2026-21513 is a high-severity vulnerability in Microsoft Windows 10 1607 with a CVSS 3.x base score of 8.8. It is listed in CISA's Known Exploited Vulnerabilities (KEV) catalog, confirming it has been exploited in the wild (added 2026-02-10). The underlying weakness is classified as CWE-693.

Key facts

Severity: High (CVSS 3.x base score 8.8)
EPSS exploit prediction: 16% (97th percentile)
Actively exploited: Yes — listed in CISA KEV (added 2026-02-10)
EU (EUVD) id: EUVD-2026-7342
EU exploitation: Flagged exploited in the ENISA EU Vulnerability Database (since 2026-02-10)
Weakness: CWE-693
Affected product: Microsoft Windows 10 1607
Published: 2026-02-10
Last modified: 2026-06-17

Description

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

Frequently asked questions

What is CVE-2026-21513?: Protection mechanism failure in MSHTML Framework allows an unauthorized attacker to bypass a security feature over a network.
How severe is CVE-2026-21513?: CVE-2026-21513 has a CVSS 3.x base score of 8.8, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2026-21513 being actively exploited?: Yes. CVE-2026-21513 is on CISA's Known Exploited Vulnerabilities (KEV) catalog, added on 2026-02-10, which means active exploitation has been confirmed. It should be prioritised for remediation.
What products are affected by CVE-2026-21513?: CVE-2026-21513 primarily affects Microsoft Windows 10 1607. In total, 23 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2026-21513?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Because this CVE is known to be actively exploited, treat remediation as urgent — CISA KEV typically sets a short remediation deadline.
Does CVE-2026-21513 have an EU (EUVD) identifier?: Yes. CVE-2026-21513 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-7342. It is also flagged as exploited in the EUVD (since 2026-02-10).
When was CVE-2026-21513 published?: CVE-2026-21513 was published on 2026-02-10 and last updated on 2026-06-17.

References

Affected products (23)

cpe:2.3:o:microsoft:windows_10_1607:*:*:*:*:*:*:x64:*
cpe:2.3:o:microsoft:windows_10_1607:*:*:*:*:*:*:x86:*
cpe:2.3:o:microsoft:windows_10_1809:*:*:*:*:*:*:x64:*
cpe:2.3:o:microsoft:windows_10_1809:*:*:*:*:*:*:x86:*
cpe:2.3:o:microsoft:windows_10_21h2:*:*:*:*:*:*:arm64:*
cpe:2.3:o:microsoft:windows_10_21h2:*:*:*:*:*:*:x64:*
cpe:2.3:o:microsoft:windows_10_21h2:*:*:*:*:*:*:x86:*
cpe:2.3:o:microsoft:windows_10_22h2:*:*:*:*:*:*:arm64:*
cpe:2.3:o:microsoft:windows_10_22h2:*:*:*:*:*:*:x64:*
cpe:2.3:o:microsoft:windows_10_22h2:*:*:*:*:*:*:x86:*
cpe:2.3:o:microsoft:windows_11_23h2:*:*:*:*:*:*:arm64:*
cpe:2.3:o:microsoft:windows_11_23h2:*:*:*:*:*:*:x64:*
cpe:2.3:o:microsoft:windows_11_24h2:*:*:*:*:*:*:arm64:*
cpe:2.3:o:microsoft:windows_11_24h2:*:*:*:*:*:*:x64:*
cpe:2.3:o:microsoft:windows_11_25h2:*:*:*:*:*:*:arm64:*
cpe:2.3:o:microsoft:windows_11_25h2:*:*:*:*:*:*:x64:*
cpe:2.3:o:microsoft:windows_server_2012:-:*:*:*:*:*:*:*
cpe:2.3:o:microsoft:windows_server_2012:r2:*:*:*:*:*:*:*
cpe:2.3:o:microsoft:windows_server_2016:*:*:*:*:-:*:x64:*
cpe:2.3:o:microsoft:windows_server_2019:*:*:*:*:-:*:x64:*
cpe:2.3:o:microsoft:windows_server_2022:*:*:*:*:-:*:x64:*
cpe:2.3:o:microsoft:windows_server_2022_23h2:*:*:*:*:-:*:x64:*
cpe:2.3:o:microsoft:windows_server_2025:*:*:*:*:*:*:x64:*

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Other CWE-693 (Protection Mechanism Failure) vulnerabilities

CVE-2026-93606 — Critical (CVSS 10.0): vm2 (npm) versions 3.12.0 and earlier contain a sandbox escape in `VM` and `NodeVM`. When an embedder exposes a host…
CVE-2026-93605 — Critical (CVSS 10.0): vm2 NodeVM versions before 3.12.1 contain a sandbox escape vulnerability where the DANGEROUS_BUILTINS denylist omits…
CVE-2026-92956 — Critical (CVSS 10.0): vm2 versions 3.10.1 through 3.11.6 contain a sandbox escape reachable from a default `new VM()` sandbox when running on…
CVE-2026-75874 — Critical (CVSS 10.0): Sandbox escape in the Remote Settings Client component. This vulnerability was fixed in Firefox 154, Thunderbird 154,…
CVE-2026-47140 — Critical (CVSS 10.0): vm2 is an open source vm/sandbox for Node.js. Prior to version 3.11.4, NodeVM blocks several dangerous Node.js builtins…
CVE-2026-34208 — Critical (CVSS 10.0): SandboxJS is a JavaScript sandboxing library. Prior to 0.8.36, SandboxJS blocks direct assignment to global objects…

Browse all CWE-693 (Protection Mechanism Failure) vulnerabilities →