CVE-2026-102862: SharePoint Server Privilege Escalation Flaw

CVE-2026-102862 Overview

CVE-2026-102862 is an incorrect authorization vulnerability [CWE-863] in Microsoft Office SharePoint Server. An authenticated attacker can abuse the flaw to elevate privileges over a network. Microsoft published the advisory on October 13, 2026, and assigned a CVSS 3.1 score of 8.8.

The vulnerability affects Microsoft SharePoint Server Subscription Edition. Successful exploitation grants the attacker higher-privileged access to SharePoint content and administrative functions. The attack requires low privileges and no user interaction.

Critical Impact
An authenticated attacker on the network can bypass authorization checks in SharePoint Server to gain elevated privileges, compromising confidentiality, integrity, and availability of hosted data and services.

Affected Products

Microsoft SharePoint Server Subscription Edition
Deployments exposing SharePoint endpoints to authenticated users on the network
SharePoint sites relying on built-in authorization checks for privilege separation

Discovery Timeline

2026-10-13 - CVE-2026-102862 published to NVD and Microsoft advisory released
2026-10-14 - Last updated in NVD database

Technical Details for CVE-2026-102862

Vulnerability Analysis

The flaw is classified as Incorrect Authorization [CWE-863]. SharePoint performs an authorization check but reaches an incorrect decision, allowing an authenticated low-privileged user to perform actions reserved for higher-privileged roles. The vulnerability is network-reachable, requires low privileges, and no user interaction, which widens the pool of potential attackers to any user with SharePoint account access.

Exploitation impacts all three security properties. An attacker can read restricted content, modify SharePoint objects, and disrupt availability of site collections or administrative features. Because SharePoint commonly stores sensitive corporate documents and integrates with identity providers, elevated access can be pivoted into broader intrusion activity.

The EPSS score of 0.698% places the vulnerability in the 52nd percentile of likelihood of near-term exploitation. No public proof-of-concept or exploitation in the wild has been reported at the time of publication.

Root Cause

The root cause is a flawed authorization decision within SharePoint request handling. The server authenticates the caller correctly but fails to enforce the appropriate privilege boundary before executing a privileged operation. Microsoft has not published implementation-level details beyond the advisory.

Attack Vector

The attack vector is network-based. An attacker with valid SharePoint credentials sends crafted requests to a vulnerable server endpoint. The server grants access to functionality or data that should be restricted, resulting in privilege elevation within the SharePoint environment. See the Microsoft CVE-2026-102862 Guidance for vendor-specific technical details.

Detection Methods for CVE-2026-102862

Indicators of Compromise

Unexpected changes to SharePoint permission levels, site collection administrators, or role assignments made by standard user accounts
Access events in SharePoint Unified Logging Service (ULS) logs where low-privileged accounts successfully invoke administrative endpoints
Anomalous HTTP requests to SharePoint administrative or API paths originating from non-administrative user sessions
Creation or modification of SharePoint apps, workflows, or event receivers by accounts without historical administrative activity

Detection Strategies

Correlate SharePoint audit events with Entra ID sign-in logs to identify privilege operations performed by accounts whose role should not permit them
Baseline normal administrative activity per site collection and alert on deviations, including off-hours administrative changes
Review web server IIS logs for high-frequency requests to privileged SharePoint handlers from authenticated non-admin accounts

Monitoring Recommendations

Enable SharePoint auditing for permission changes, security policy changes, and content modifications across all site collections
Forward SharePoint ULS and IIS logs to a centralized SIEM for correlation with identity telemetry
Monitor for new or modified farm-level solutions, features, and administrative configuration changes

How to Mitigate CVE-2026-102862

Immediate Actions Required

Apply the Microsoft security update referenced in the Microsoft CVE-2026-102862 Guidance to all SharePoint Server Subscription Edition instances
Inventory SharePoint accounts and remove unnecessary access to reduce the pool of users who could abuse the authorization flaw
Review recent SharePoint audit logs for privilege changes performed by non-administrative accounts

Patch Information

Microsoft has released a security update addressing CVE-2026-102862. Administrators should install the update on all SharePoint Server Subscription Edition servers in the farm, following the standard SharePoint patching sequence of binary installation followed by the SharePoint Products Configuration Wizard or PSConfig on every server. Verify farm build numbers post-patch to confirm successful deployment.

Workarounds

No vendor-supplied workaround is listed; apply the security update as the primary remediation
Restrict network access to SharePoint endpoints so only trusted users and services can authenticate
Enforce multifactor authentication for all SharePoint accounts to reduce the risk of attacker-controlled credentials being used for exploitation
Apply the principle of least privilege for SharePoint site, farm, and shell administrator roles

bash

# After installing the SharePoint security update on each server in the farm,
# run the configuration wizard to apply schema and binary changes.
PSConfig.exe -cmd upgrade -inplace b2b -wait -cmd applicationcontent -install -cmd installfeatures

# Verify the farm build version post-patch
Get-SPFarm | Select-Object BuildVersion