CVE-2025-29794 Overview
CVE-2025-29794 is an improper authorization vulnerability in Microsoft Office SharePoint Server. An authenticated attacker can exploit the flaw to execute arbitrary code over the network against affected SharePoint deployments. The vulnerability is tracked under CWE-285: Improper Authorization and carries a CVSS 3.1 score of 8.8.
The affected products include Microsoft SharePoint Server 2016, 2019, and SharePoint Server Subscription Edition. Microsoft published a security update addressing the issue through its Security Update Guide.
Critical Impact
Authenticated attackers can execute arbitrary code on SharePoint servers across the network, compromising confidentiality, integrity, and availability of hosted content and connected systems.
Affected Products
- Microsoft SharePoint Enterprise Server 2016
- Microsoft SharePoint Server 2019
- Microsoft SharePoint Server Subscription Edition
Discovery Timeline
- 2025-04-08 - CVE-2025-29794 published to NVD
- 2025-07-09 - Last updated in NVD database
Technical Details for CVE-2025-29794
Vulnerability Analysis
The vulnerability stems from improper authorization checks within Microsoft Office SharePoint Server. A user holding low-privilege credentials can submit crafted requests that bypass authorization boundaries enforced by SharePoint. The bypass allows the attacker to invoke functionality or reach code paths that should be restricted to higher-privilege roles.
Successful exploitation results in remote code execution in the context of the SharePoint service account. Because SharePoint commonly runs with elevated privileges and integrates with backend services, code execution on the server typically translates to broader access across the farm. The attack requires no user interaction and can be conducted entirely over the network.
The EPSS model assigns this issue a probability of 0.486% (percentile 65.5), reflecting moderate predicted exploitation interest relative to other published CVEs.
Root Cause
The root cause is an authorization flaw classified as [CWE-285]. SharePoint fails to consistently validate that an authenticated principal is permitted to invoke a specific operation. The missing check permits an authorized but low-privilege user to reach privileged execution flows that normally require administrative rights.
Attack Vector
The attack vector is network-based. An attacker authenticates to SharePoint with any valid account, then issues a crafted request that triggers the unauthorized code path. The request executes code on the server with the privileges of the SharePoint application pool identity, enabling installation of web shells, theft of stored content, or lateral movement through the farm.
No public proof-of-concept code is currently available, and the issue is not listed in the CISA Known Exploited Vulnerabilities catalog. Refer to the Microsoft Security Update Guide for vendor-supplied technical details.
Detection Methods for CVE-2025-29794
Indicators of Compromise
- Unexpected w3wp.exe child processes such as cmd.exe, powershell.exe, or csc.exe spawned by SharePoint application pools.
- New or modified .aspx, .ashx, or .asmx files in SharePoint web application directories under C:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\.
- Anomalous HTTP POST requests to SharePoint endpoints originating from low-privilege user accounts.
- Outbound network connections from SharePoint servers to unknown external hosts.
Detection Strategies
- Hunt for process chains where the SharePoint worker process spawns scripting interpreters or shell binaries.
- Review IIS logs for repeated requests to SharePoint handlers from a single authenticated user across short time windows.
- Correlate Windows Security Event ID 4688 (process creation) with SharePoint Unified Logging Service (ULS) entries to identify unauthorized API calls.
Monitoring Recommendations
- Forward IIS, ULS, and Windows Event Logs from all SharePoint servers to a centralized SIEM for retention and analytics.
- Baseline normal SharePoint administrative actions and alert on deviations such as new web parts, feature activations, or solution deployments from non-admin accounts.
- Monitor file integrity on the SharePoint hive and _layouts directories for unauthorized changes.
How to Mitigate CVE-2025-29794
Immediate Actions Required
- Apply the Microsoft security updates referenced in the MSRC advisory to all SharePoint Server 2016, 2019, and Subscription Edition instances.
- Inventory SharePoint farms and confirm patch level on every web front-end and application server before resuming normal operations.
- Audit SharePoint user accounts and remove standing access that is no longer required, reducing the population of accounts able to authenticate.
- Rotate credentials for the SharePoint farm account and any service accounts if compromise is suspected.
Patch Information
Microsoft released cumulative security updates for SharePoint Server 2016, SharePoint Server 2019, and SharePoint Server Subscription Edition that address CVE-2025-29794. Administrators should follow the version-specific KB articles listed in the Microsoft Security Update Guide and reboot servers as instructed. Verify that the Antimalware Scan Interface (AMSI) integration is enabled after patching.
Workarounds
- Enable AMSI integration in SharePoint and ensure Microsoft Defender Antivirus or an equivalent solution is running on every SharePoint server.
- Restrict network access to SharePoint web applications using firewall rules and reverse proxies, limiting reachability to authenticated corporate networks only.
- Enforce least-privilege role assignments within SharePoint sites and remove anonymous or broadly scoped permissions.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
