How severe is CVE-2026-64921?

CVE-2026-64921 has a CVSS 3.x base score of 8.8, rated high severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2026-64921 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (60th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-64921?

CVE-2026-64921 primarily affects Microsoft Sharepoint Server. In total, 3 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2026-64921?

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

When was CVE-2026-64921 published?

CVE-2026-64921 was published on 2026-08-11 and last updated on 2026-08-13.

CVE-2026-64921

CVE-2026-64921 is a high-severity vulnerability in Microsoft Sharepoint Server with a CVSS 3.x base score of 8.8. 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-306.

Key facts

Severity: High (CVSS 3.x base score 8.8)
EPSS exploit prediction: 1% (60th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-306
Affected product: Microsoft Sharepoint Server
Published: 2026-08-11
Last modified: 2026-08-13

Description

Missing authentication for critical function in Microsoft Office SharePoint allows an authorized attacker to elevate privileges over a network.

Frequently asked questions

What is CVE-2026-64921?: Missing authentication for critical function in Microsoft Office SharePoint allows an authorized attacker to elevate privileges over a network.
How severe is CVE-2026-64921?: CVE-2026-64921 has a CVSS 3.x base score of 8.8, rated high severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2026-64921 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (60th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-64921?: CVE-2026-64921 primarily affects Microsoft Sharepoint Server. In total, 3 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2026-64921?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2026-64921 published?: CVE-2026-64921 was published on 2026-08-11 and last updated on 2026-08-13.

References

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-64921

Affected products (3)

cpe:2.3:a:microsoft:sharepoint_server:*:*:*:*:subscription:*:*:*
cpe:2.3:a:microsoft:sharepoint_server:2016:*:*:*:enterprise:*:*:*
cpe:2.3:a:microsoft:sharepoint_server:2019:*:*:*:*:*:*:*

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