CVE-2026-42832 — Microsoft Office Improper Access Control Vulnerability Leading to Spoofing

CVE-2026-42832 is an improper access control vulnerability affecting Microsoft Office. An attacker could exploit this vulnerability to perform spoofing actions locally. The vulnerability exists due to a flaw in how Microsoft Office handles access controls, allowing an unauthorized user to potentially impersonate or misrepresent themselves within the application. This could lead to users being tricked into performing actions they wouldn’t normally, such as providing credentials or opening malicious documents. The scope of the vulnerability is limited to local exploitation, meaning the attacker needs to have some level of access to the affected system.

Attack Chain

1. Attacker gains local access to a system with vulnerable Microsoft Office.
2. Attacker crafts a malicious Office document or uses an existing one.
3. The malicious document leverages the improper access control vulnerability.
4. The user opens the malicious document locally in Microsoft Office.
5. The vulnerability is triggered, granting the attacker elevated privileges.
6. The attacker spoofs a trusted entity or feature within Microsoft Office.
7. The user is tricked into performing an action (e.g., entering credentials).

Impact

Successful exploitation of CVE-2026-42832 could allow an attacker to perform convincing spoofing attacks, potentially leading to credential theft, data breaches, or other malicious activities. The impact is primarily limited to the local system, but if the user has elevated privileges, the attacker could potentially gain further access to network resources.

Recommendation

• Apply the Microsoft patch referenced in https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-42832 to remediate CVE-2026-42832.
• Deploy the Sigma rule “Detect Suspicious Office Process Creation” to identify potential exploitation attempts related to this vulnerability based on spawned processes.
• Monitor for unusual file modifications or registry changes associated with Microsoft Office applications, as these could indicate exploitation.