How severe is CVE-2021-42309?

CVE-2021-42309 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-2021-42309 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 3% (84th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-42309?

CVE-2021-42309 primarily affects Microsoft Sharepoint Enterprise Server. In total, 4 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-42309?

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-2021-42309 published?

CVE-2021-42309 was published on 2021-12-15 and last updated on 2026-06-17.

CVE-2021-42309

CVE-2021-42309 is a high-severity vulnerability in Microsoft Sharepoint Enterprise 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-94.

Key facts

Severity: High (CVSS 3.x base score 8.8)
CVSS v2: 6.5
EPSS exploit prediction: 3% (84th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-94
Affected product: Microsoft Sharepoint Enterprise Server
Published: 2021-12-15
Last modified: 2026-06-17

Description

Microsoft SharePoint Server Remote Code Execution Vulnerability

Frequently asked questions

What is CVE-2021-42309?: Microsoft SharePoint Server Remote Code Execution Vulnerability
How severe is CVE-2021-42309?: CVE-2021-42309 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-2021-42309 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 3% (84th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-42309?: CVE-2021-42309 primarily affects Microsoft Sharepoint Enterprise Server. In total, 4 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-42309?: 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-2021-42309 published?: CVE-2021-42309 was published on 2021-12-15 and last updated on 2026-06-17.

References

Affected products (4)

cpe:2.3:a:microsoft:sharepoint_enterprise_server:2016:*:*:*:*:*:*:*
cpe:2.3:a:microsoft:sharepoint_foundation:2013:sp1:*:*:*:*:*:*
cpe:2.3:a:microsoft:sharepoint_server:-:*:*:*:subscription:*:*:*
cpe:2.3:a:microsoft:sharepoint_server:2019:*:*:*:*:*:*:*

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