How severe is CVE-2025-21311?

CVE-2025-21311 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2025-21311 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (81st percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2025-21311?

CVE-2025-21311 primarily affects Microsoft Windows 11 24h2. In total, 3 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2025-21311?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

Does CVE-2025-21311 have an EU (EUVD) identifier?

Yes. CVE-2025-21311 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-2376.

When was CVE-2025-21311 published?

CVE-2025-21311 was published on 2025-01-14 and last updated on 2026-06-17.

CVE-2025-21311

CVE-2025-21311 is a critical-severity vulnerability in Microsoft Windows 11 24h2 with a CVSS 3.x base score of 9.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-303.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
EPSS exploit prediction: 2% (81st percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2025-2376
Weakness: CWE-303
Affected product: Microsoft Windows 11 24h2
Published: 2025-01-14
Last modified: 2026-06-17

Description

Windows NTLM V1 Elevation of Privilege Vulnerability

Frequently asked questions

What is CVE-2025-21311?: Windows NTLM V1 Elevation of Privilege Vulnerability
How severe is CVE-2025-21311?: CVE-2025-21311 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2025-21311 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (81st percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2025-21311?: CVE-2025-21311 primarily affects Microsoft Windows 11 24h2. In total, 3 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2025-21311?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
Does CVE-2025-21311 have an EU (EUVD) identifier?: Yes. CVE-2025-21311 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-2376.
When was CVE-2025-21311 published?: CVE-2025-21311 was published on 2025-01-14 and last updated on 2026-06-17.

References

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2025-21311

Affected products (3)

cpe:2.3:o:microsoft:windows_11_24h2:*:*:*:*:*:*:*:*
cpe:2.3:o:microsoft:windows_server_2022_23h2:*:*:*:*:*:*:*:*
cpe:2.3:o:microsoft:windows_server_2025:*:*:*:*:*:*:x64:*

More vulnerabilities in Microsoft Windows 11 24h2

CVE-2026-57092 — Critical (CVSS 9.9): Use after free in Windows VMSwitch allows an authorized attacker to elevate privileges over a network.
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CVE-2026-62815 — Critical (CVSS 9.8): Use after free in Microsoft QUIC allows an unauthorized attacker to execute code over a network.
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