Microsoft SharePoint Server Elevation of Privilege Vulnerability

Source data

Overview

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

Impact & technical details

Elevation of Privilege

According to the CVSS metric, the attack vector is network (AV:N) and the attack complexity is low (AC:L). What does that mean for this vulnerability? The attack vector is Network (AV:N) because this vulnerability is remotely exploitable and can be exploited from the internet. The attack complexity is Low (AC:L) because an attacker does not require significant prior knowledge of the system and can achieve repeatable success with the payload against the vulnerable component.

I am running SharePoint Server 2016. Do the updates for SharePoint Enterprise Server 2016 also apply to the version I am running? Yes. The same KB number applies to both SharePoint Server 2016 and SharePoint Enterprise Server 2016. Customers running either version should install the security update to be protected from this vulnerability.

CVSS base score

5.3 / 10

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N/E:F/RL:O/RC:C

Highest base score supplied by MSRC for this record; the vector belongs to that score. Ratings can vary by product. Microsoft Important is displayed as High; Moderate is displayed as Medium.

Affected products

• Microsoft SharePoint Enterprise Server 2016
• Microsoft SharePoint Server 2019
• Microsoft SharePoint Server Subscription Edition

Source guidance

Remediation

• The following mitigating factors might be helpful in your situation: Enable AMSI: Ensure the Antimalware Scan Interface (AMSI) is actively integrated and scanning SharePoint and IIS worker process memory. Enable AMSI scan feature and set the Request Body Scan mode to Full in order for POST body payloads to be detected. Configure AMSI integration with SharePoint Server - https://learn.microsoft.com/en-us/sharepoint/security-for-sharepoint-server/configure-amsi-integration
• Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.

At least one Microsoft vendor-fix reference is available. Check each affected product for its applicable update, prerequisites, and supported version.

Authoritative sources & updates

Findings and update information come from the linked publishers. GTP compiles the public record and provides the recommendation above. CVSS ratings shown here come from Microsoft. NVD references provide additional public context.

• Microsoft Security Response Center (opens in a new tab)
• Microsoft security update · 5002891 (opens in a new tab)
• Microsoft remediation guidance (opens in a new tab)
• Microsoft security update · 5002883 (opens in a new tab)
• Microsoft remediation guidance (opens in a new tab)
• Microsoft security update · 5002882 (opens in a new tab)
• Microsoft remediation guidance (opens in a new tab)
• CISA Known Exploited Vulnerabilities (opens in a new tab)
• Authoritative advisory (opens in a new tab)
• Authoritative advisory (opens in a new tab)
• Authoritative advisory (opens in a new tab)
• NIST National Vulnerability Database (opens in a new tab)