CVE-2026-62827: SharePoint Server Privilege Escalation Flaw

CVE-2026-62827 Overview

CVE-2026-62827 is an improper authentication vulnerability [CWE-287] in Microsoft Office SharePoint Server. An authorized attacker can elevate privileges over a network by exploiting weaknesses in how SharePoint validates authenticated sessions. The flaw affects SharePoint Server Subscription Edition, SharePoint Server 2019, and SharePoint Server 2016 Enterprise. Microsoft published the advisory on August 11, 2026, and the entry was last modified on August 12, 2026. Successful exploitation impacts confidentiality, integrity, and availability across the SharePoint deployment.

Critical Impact
An authenticated attacker with low privileges can escalate to higher-privileged roles across a SharePoint farm, gaining broad access to site collections, content, and administrative functions.

Affected Products

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

Discovery Timeline

2026-08-11 - CVE-2026-62827 published to NVD
2026-08-11 - Microsoft releases security update for CVE-2026-62827
2026-08-12 - Last updated in NVD database

Technical Details for CVE-2026-62827

Vulnerability Analysis

CVE-2026-62827 stems from improper authentication logic within Microsoft SharePoint Server. The server fails to correctly enforce identity or role boundaries for an authenticated request, permitting an attacker holding valid low-privilege credentials to perform actions reserved for higher-privileged users. Because SharePoint centralizes document storage, workflows, and collaboration for many enterprises, privilege escalation on a single server can expose sensitive content and grant control over configuration.

The vulnerability requires network access to the SharePoint endpoint and prior authentication. No user interaction is required, and exploitation complexity is low. The Exploit Prediction Scoring System (EPSS) rates this issue at 0.604% as of August 13, 2026.

Root Cause

The root cause is classified under CWE-287 (Improper Authentication). SharePoint accepts authenticated requests without adequately verifying the caller's authorization to perform the requested privileged operation. This gap in identity verification allows a valid session or token to be reused or extended beyond its intended scope, breaking the separation between standard users and privileged roles.

Attack Vector

The attack vector is network-based. An attacker first obtains valid credentials on the target SharePoint instance, then issues a crafted request against the vulnerable endpoint. The request bypasses the authentication check that should restrict the operation to administrators or site owners, causing SharePoint to execute the operation under elevated context. Public proof-of-concept code is not available at the time of publication, and CVE-2026-62827 is not listed in the CISA Known Exploited Vulnerabilities catalog.

No verified public exploit code is available. Refer to the Microsoft Security Update for CVE-2026-62827 for the technical description provided by the vendor.

Detection Methods for CVE-2026-62827

Indicators of Compromise

Unexpected role assignments or permission changes on SharePoint site collections, particularly promotions to Site Collection Administrator.
Authenticated requests from standard user accounts targeting administrative endpoints such as _layouts/15/ administrative pages or SOAP/CSOM APIs used for permission management.
New farm-level or web-application-level policy entries added outside of normal change windows.
Anomalous access patterns from low-privilege accounts touching content databases or configuration lists.

Detection Strategies

Enable and forward SharePoint Unified Logging Service (ULS) logs and IIS logs to a centralized analytics platform for correlation.
Alert on privilege change events (SPRoleAssignment modifications, group membership changes) initiated by non-administrative principals.
Baseline normal API usage per user role and flag authenticated calls to privileged endpoints from accounts that have never used them.
Correlate authentication events with subsequent administrative actions to identify low-privilege sessions performing high-privilege operations.

Monitoring Recommendations

Monitor Windows Security Event Log for account elevation events on SharePoint servers, including Event IDs 4672 and 4728.
Track outbound and inbound traffic to SharePoint web front ends for authenticated request bursts from single accounts.
Review scheduled tasks, timer jobs, and feature activations added after August 11, 2026, on any SharePoint server not yet patched.
Enable audit logging in Central Administration for site collections holding sensitive content.

How to Mitigate CVE-2026-62827

Immediate Actions Required

Apply the Microsoft security update referenced in the MSRC advisory for CVE-2026-62827 to all SharePoint Server 2016, 2019, and Subscription Edition instances.
Inventory all SharePoint farms and confirm patch level on every web front end, application server, and search server.
Rotate credentials for service accounts and administrative accounts that authenticate to SharePoint during the exposure window.
Review recent permission changes and audit logs to identify potential prior exploitation.

Patch Information

Microsoft published the security update on August 11, 2026. Administrators should install the update via the Microsoft Update Catalog or standard patch management tooling. See the Microsoft Security Update for CVE-2026-62827 for build numbers, KB identifiers, and download links applicable to each SharePoint version.

Workarounds

Restrict network access to SharePoint web front ends to trusted corporate networks and VPN ranges until patching completes.
Enforce multi-factor authentication for all SharePoint user accounts to reduce the pool of credentials available to attackers.
Temporarily disable self-service site creation and limit permission management to a small set of dedicated administrative accounts.
Increase audit log retention and review frequency on unpatched systems.

bash

# Example: verify installed SharePoint patch level on Windows Server
Get-SPProduct | Select-Object ProductName, PatchableUnitDisplayName, PatchableUnitVersion

# Restrict access at the firewall to trusted subnets (example using Windows Firewall)
New-NetFirewallRule -DisplayName "SharePoint Restrict 443" -Direction Inbound -Protocol TCP -LocalPort 443 -RemoteAddress 10.0.0.0/8 -Action Allow