Critical Deserialization Vulnerability in Microsoft SharePoint (CVE‑2026‑20963) Threatens Enterprise Collaboration
What It Is – A remote‑code‑execution (RCE) flaw in Microsoft SharePoint allows an attacker to deserialize untrusted data, leading to arbitrary code execution on the SharePoint server. The vulnerability is tracked as CVE‑2026‑20963 and has been confirmed as actively exploited in the wild.
Exploitability – Exploits are observed in the wild; a proof‑of‑concept exists and threat actors are leveraging the flaw to gain footholds in victim environments. The CVSS v3.1 base score is 8.8 (High).
Affected Products – Microsoft SharePoint Server (on‑premises) and SharePoint Online components that process serialized objects.
TPRM Impact – Organizations that rely on SharePoint as a collaboration platform—whether hosted internally or via Microsoft 365—face supply‑chain risk. A compromised SharePoint instance can be used to pivot into partner networks, exfiltrate proprietary documents, and embed malicious payloads that affect downstream vendors.
Recommended Actions –
- Verify the presence of the vulnerable SharePoint version across all environments.
- Apply Microsoft’s security update (KB xxxxxx) immediately; prioritize remediation per CISA BOD 22‑01 deadlines.
- Conduct a focused vulnerability scan on third‑party‑managed SharePoint sites.
- Review and tighten deserialization handling in custom SharePoint solutions.
- Update incident‑response playbooks to include detection of exploitation attempts (e.g., anomalous web‑request patterns).
Source: CISA Advisory – CISA Adds One Known Exploited Vulnerability to Catalog (2026‑03‑18)