Microsoft SharePoint Weak Authentication Bypass Vulnerability
Actively exploited in the wild. Patch or mitigate immediately — don't wait for a maintenance window.
An unauthenticated attacker, remotely over the network, with no user interaction, can steal data and tamper with data.
Weak authentication in Microsoft Office SharePoint allows an unauthorized attacker to bypass a security feature over a network.
Inferred from the weakness type (CWE) and how the flaw is reached — the techniques an attacker would chain to exploit this. Real-world corroboration appears here as threat intel is folded in.
Corroborated threat activity referencing this CVE — with source and confidence, not inference.
Named threat actors and observed ATT&CK techniques appear here as intel feeds are folded in — the ATT&CK chain above stays inferred until then.
Generated by Wavense from the CVE record — an immediate mitigation and the permanent fix.
Isolate SharePoint servers using strict network segmentation and firewall rules to restrict access to trusted networks only. Enforce multi-factor authentication (MFA) for all SharePoint users and administrators, and review existing access controls to ensure the principle of least privilege is strictly applied. Implement robust monitoring of SharePoint access logs for any suspicious or unauthorized login attempts.
Apply the official security updates and patches released by Microsoft for SharePoint Server as soon as they become available. Ensure all affected SharePoint instances are upgraded to the specific version that contains the fix for CVE-2026-55040 to permanently address the weak authentication vulnerability and prevent future exploitation.
An unauthorized attacker can exploit this weak authentication to bypass security features over a network, gaining complete access to sensitive SharePoint data and functionalities. This could lead to severe data breaches, system compromise, and significant operational disruption, incurring substantial financial and reputational damage to the organization.
Other CVEs affecting sharepoint server
Deserialization of untrusted data in Microsoft Office SharePoint allows an unauthorized attacker to execute code over a network.
Deserialization of untrusted data in Microsoft Office SharePoint allows an unauthorized attacker to execute code over a network.
Deserialization of untrusted data in Microsoft Office SharePoint allows an unauthorized attacker to execute code over a network.
Deserialization of untrusted data in on-premises Microsoft SharePoint Server allows an unauthorized attacker to execute code over a network. Microsoft is aware that an exploit for CVE-2025-53770 exists in the wild. Microsoft is preparing and fully testing a comprehensive update to address this vulnerability. In the meantime, please make sure that the mitigation provided in this CVE documentation is in place so that you are protected from exploitation.
Microsoft SharePoint Server Elevation of Privilege Vulnerability
A remote code execution vulnerability exists in Microsoft SharePoint when the software fails to check the source markup of an application package, aka 'Microsoft SharePoint Remote Code Execution Vulnerability'. This CVE ID is unique from CVE-2019-0594.