CVE Alert: CVE-2025-49706 – Microsoft – Microsoft SharePoint Enterprise Server 2016

Risk verdict

Active exploitation of a remote spoofing flaw in an on-premises collaboration platform has been identified; treat as priority 1 given KEV presence.

Why this matters

The flaw enables spoofed authentication over the network without user interaction, risking access to restricted content and impersonation of legitimate users. In organisations with sensitive data or regulated workflows, this can lead to data leakage, tampered documents, or trust exploitation, especially where external exposure and broad internal access exist.

Most likely attack path

Preconditions are minimal: remote, network‑based access with no authentication required and no user interaction. An attacker could initiate spoofing attempts directly against the on‑premises gateway, then access or manipulate content under the guise of legitimate identities, potentially enabling lateral movement within the trusted network if weak segmentation exists.

Who is most exposed

Organisations with internet‑facing instances of the platform and weak network controls, including insufficient MFA or conditional access, are at higher risk. Legacy or unpatched deployments in large enterprises are particularly vulnerable.

Detection ideas

• Anomalous authentication events: successful logins from unusual identities or locations.
• Suspicious HTTP request patterns or headers suggesting identity spoofing.
• Access to restricted resources from anomalous user accounts or sessions.
• Unusual growth in outbound data or access to sensitive documents during off hours.
• Logs showing rapid sequence of access attempts without user prompts.

Mitigation and prioritisation

• Apply the vendor patch immediately; treat as priority 1 due to KEV exploitation.
• Implement network access controls to limit exposure (restrict external access, deploy WAF rules).
• Enforce strong authentication/conditional access and MFA where possible.
• Improve segmentation and least-privilege rights; isolate sensitive content.
• Document patch window and monitor closely post‑deployment; enable continuous logging and alerting.