CVE-2026-47294: OS Command Injection in Microsoft SharePoint Server – Critical Update

Technical summary

CVE-2026-47294 is an OS command injection vulnerability (CWE-78) in Microsoft SharePoint Server that stems from improper neutralization of special elements in OS command construction. The vulnerability has a CVSS 3.1 score of 8.0 (High severity) with a vector of CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H, indicating network accessibility, low attack complexity, and requirement for low-level privileges. An authorized attacker can supply specially formatted input that bypasses input validation mechanisms, allowing arbitrary OS commands to execute in the context of the SharePoint application. The vulnerability affects multiple versions of Microsoft SharePoint Server.

Business impact

Compromise of SharePoint infrastructure through this vulnerability could enable attackers to access, modify, or exfiltrate sensitive documents and collaboration data stored within the platform. Depending on the attacker's objectives and the data sensitivity, this could result in intellectual property theft, regulatory compliance violations, business disruption, or lateral movement to other enterprise systems. Organizations using SharePoint for business-critical workflows should treat this as a significant operational risk until patches are deployed.

Affected systems

This vulnerability affects multiple versions of Microsoft SharePoint Server as listed in Microsoft's official advisory. Organizations running SharePoint Server in on-premises or hybrid deployments should verify which specific versions are deployed in their environment against the vendor advisory to determine exposure. SharePoint Online (cloud-based) may have different remediation timelines; verify current status with Microsoft's advisory documentation.

Exploitability

While the vulnerability requires an authenticated attacker with valid SharePoint user credentials and involves user interaction (UI:R in the CVSS vector), the low attack complexity and network accessibility make it moderately exploitable once an attacker gains initial access. The barrier to exploitation is the prerequisite of valid credentials; however, credential compromise is a common precursor in targeted attacks. This is not currently listed on CISA's Known Exploited Vulnerabilities (KEV) catalog, but organizations should assume active research and potential exploitation are ongoing.

Remediation

Apply security updates from Microsoft for affected SharePoint Server versions as soon as feasible within your change management process. Verify the specific patch versions applicable to your deployment through the Microsoft advisory. Additionally, implement network segmentation to restrict SharePoint administrative and user access to trusted networks where possible. Review and enforce principle of least privilege for SharePoint account permissions to limit the blast radius of successful exploitation.

Patch guidance

Consult the official Microsoft advisory associated with CVE-2026-47294 for the specific cumulative update or security patch version applicable to your SharePoint Server version and build. Test patches in a non-production environment before deployment to production systems. Coordinate with SharePoint administrators and stakeholders on maintenance windows, as patches may require service restarts. Verify patch application by confirming the updated build numbers and re-scanning with your vulnerability assessment tools post-deployment.

Detection guidance

Monitor SharePoint logs and IIS logs for suspicious command execution patterns, unusual process spawning from the SharePoint application pool identity, and unexpected child processes launched by w3wp.exe or owstimer.exe. Implement application-level alerting for SharePoint input validation failures and OS command injection attempts. Consider endpoint detection and response (EDR) solutions to alert on anomalous process activity originating from SharePoint application pools. Network-based intrusion detection systems may flag exploitation attempts with unusual SharePoint request payloads.

Why prioritize this

This vulnerability warrants high priority remediation due to its High CVSS severity score (8.0), the sensitive nature of data typically stored in SharePoint, and the direct path to code execution. Although it requires authentication, the low attack complexity and the likelihood of credential compromise in phishing or lateral movement attacks mean this should not be deprioritized. Organizations should address this within 30 days of patch availability, or sooner if SharePoint is exposed to untrusted networks or contains highly sensitive data.

Risk score, explained

The CVSS 3.1 score of 8.0 reflects the combination of network-based attack vector, low attack complexity, requirement for low-level privileges (authenticated user), user interaction needed, and high impact on confidentiality, integrity, and availability. The score appropriately captures that while some friction exists (authentication, user interaction), the ease of exploitation and severity of potential impact justify the High severity rating. Organizations should not downgrade priority based on the authentication requirement alone, given common credential compromise vectors.

Frequently asked questions