This vulnerability, identified as CVE-2026-42901, is an origin validation error in Microsoft Entra ID. It enables an attacker without prior privileges to elevate their privileges remotely over a network. The vulnerability has a CVSS 3.1 base score of 10.0, indicating critical severity with network attack vector, low attack complexity, no privileges required, no user interaction, and complete impact on confidentiality, integrity, and availability. Microsoft has issued an official fix for this vulnerability as documented in their security advisory.

An attacker can exploit this origin validation error to gain elevated privileges remotely, potentially leading to full compromise of the affected Microsoft Entra ID environment. The impact includes complete loss of confidentiality, integrity, and availability of the system.

Microsoft has released an official fix for this vulnerability. Users should apply the patch as soon as possible by following the guidance in the Microsoft security advisory at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-42901. No additional mitigations are indicated beyond applying the official update.