This week our CVE of the Week is CVE-2026-56164, a zero-day Elevation of Privilege vulnerability affecting Microsoft SharePoint Server that Microsoft confirmed is being actively exploited in the wild.

SharePoint is a critical business platform used for document management, collaboration, and workflow automation. As it often stores sensitive corporate data and is closely integrated with enterprise infrastructure, vulnerabilities affecting SharePoint have historically been high-value targets for attackers.

According to Microsoft, CVE-2026-56164 can be exploited with low attack complexity and without requiring existing privileges, making it particularly attractive for threat actors seeking to establish a foothold or expand access within targeted environments.

The vulnerability stands out not only because of its severity but also because exploitation was observed before patches became widely available. This significantly increases the risk for organizations running on-premises SharePoint deployments.

The U.S. Cybersecurity and Infrastructure Security Agency (CISA) has urged organizations to harden their SharePoint environments and rapidly deploy security updates in response to ongoing exploitation activity.

Recommended actions:

Apply the latest Microsoft SharePoint security updates immediately.
Prioritize remediation of internet-facing SharePoint servers.
Review SharePoint, IIS, and Windows logs for suspicious activity.
Hunt for indicators of compromise and unauthorized privilege changes.
Follow Microsoft’s and CISA’s hardening guidance for SharePoint deployments.

For more information:
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-56164

White Hat IT Security is a Europe-based Managed Security Services Provider (MSSP) and proud Microsoft Solution Partner. Its Microsoft-verified managed security solutions (MXDR) reflect their deep expertise and commitment to excellence in cybersecurity. The company was awarded the Partner of the Year Hungary Award by Microsoft in 2024 and 2025.

With the largest incident response capacity in the CEE region, they’re trusted by organizations to deliver fast, effective, and proactive protection. Their portfolio includes penetration testing, vulnerability assessments, managed Cyber Threat Intelligence, as well as Governance, Risk and Compliance (GRC) consulting and specialized security training.

They are committed to supporting professional initiatives that aim to raise cybersecurity awareness and maturity—both for individuals and organizations. They regularly contribute to the community through knowledge sharing, education, and outreach, helping to build a safer digital future for all.