CVE-2026-62917 Overview
CVE-2026-62917 is an improper input validation vulnerability in Microsoft Office SharePoint. An authorized attacker can leverage this flaw to perform spoofing attacks over a network. The vulnerability affects SharePoint Server Subscription Edition, SharePoint Server 2019, and SharePoint Server 2016 Enterprise.
Exploitation requires low privileges and user interaction, which reduces the risk profile. The vulnerability is categorized under [CWE-20] Improper Input Validation. Microsoft published guidance through the Microsoft Security Response Center (MSRC).
Critical Impact
An authenticated attacker on the network can craft input that bypasses validation to spoof content or identity within SharePoint, potentially misleading users into trusting attacker-controlled data.
Affected Products
- Microsoft SharePoint Server Subscription Edition
- Microsoft SharePoint Server 2019
- Microsoft SharePoint Server 2016 Enterprise
Discovery Timeline
- 2026-08-11 - CVE-2026-62917 published to NVD
- 2026-08-13 - Last updated in NVD database
Technical Details for CVE-2026-62917
Vulnerability Analysis
The flaw resides in how Microsoft SharePoint Server validates input supplied through network-accessible interfaces. SharePoint fails to correctly sanitize or verify specific fields before rendering or processing them. This allows an authenticated attacker to inject crafted content that appears legitimate to other users.
The result is a spoofing condition. Users may be deceived into interacting with attacker-controlled data that appears to originate from a trusted SharePoint resource. Impact on confidentiality and integrity is limited, and availability is unaffected.
Microsoft classifies this issue as a spoofing vulnerability rather than remote code execution. The scope remains unchanged, so exploitation does not cross security boundaries beyond the SharePoint application context.
Root Cause
The root cause is improper input validation [CWE-20] within SharePoint request handling. SharePoint accepts data from an authorized user without enforcing sufficient constraints on structure, encoding, or content. Downstream consumers of that data treat it as trusted, enabling spoofed output.
Attack Vector
The attack vector is network-based. An attacker must hold a valid SharePoint account with low privileges. The attacker submits crafted input to a SharePoint endpoint, then relies on user interaction, such as a victim viewing a page or clicking a link, to trigger the spoofed content.
No public proof-of-concept exploit is available at this time. The vulnerability is not listed in the CISA Known Exploited Vulnerabilities catalog. Refer to the Microsoft Security Update CVE-2026-62917 advisory for technical details.
Detection Methods for CVE-2026-62917
Indicators of Compromise
- Unusual SharePoint list, document, or page edits from accounts with limited historical activity.
- Web requests to SharePoint containing unexpected HTML, script fragments, or encoded characters in user-controlled fields.
- User reports of SharePoint content that appears misattributed or displays unexpected sender or author information.
Detection Strategies
- Review SharePoint Unified Logging Service (ULS) logs for input validation warnings and malformed request patterns.
- Correlate authentication logs with content modification events to identify low-privilege accounts making unexpected changes.
- Inspect IIS request logs on SharePoint front-end servers for anomalous query strings and POST payloads targeting list and page endpoints.
Monitoring Recommendations
- Enable SharePoint audit logging for content edits, item updates, and permission changes.
- Forward SharePoint and IIS logs to a centralized SIEM for correlation against user behavior baselines.
- Alert on repeated failed input validation events tied to a single account or source IP address.
How to Mitigate CVE-2026-62917
Immediate Actions Required
- Apply the Microsoft security update referenced in the MSRC advisory to all affected SharePoint Server installations.
- Inventory SharePoint Server deployments and confirm patch status for Subscription Edition, 2019, and 2016 Enterprise.
- Review recent content changes made by low-privilege accounts and validate their legitimacy with content owners.
Patch Information
Microsoft has released a security update for CVE-2026-62917. Administrators should install the update through the standard Windows Update or WSUS channel. Full details and download links are available in the Microsoft Security Update CVE-2026-62917 advisory.
Workarounds
- Restrict SharePoint contribution rights to trusted users where feasible until patching is complete.
- Educate users to verify the authenticity of unexpected SharePoint content before interacting with links or attachments.
- Enforce multi-factor authentication on SharePoint accounts to reduce the risk of attacker access via credential theft.
# Verify SharePoint patch level on the server
Get-SPProduct -Local | Select-Object ProductName, PatchableUnitDisplayName, Patches
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
