CVE-2018-0907 in Excel
Summary
by MITRE
Microsoft Excel 2007 SP3, Microsoft Excel 2010 SP2, Microsoft Excel 2013 SP1, Microsoft Excel 2016, Microsoft Office 2016 Click-to-Run and Microsoft Office 2016 for Mac allow a security feature bypass vulnerability due to how macro settings are enforced, aka "Microsoft Office Excel Security Feature Bypass".
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Analysis
by VulDB Data Team • 02/04/2021
This vulnerability affects multiple versions of Microsoft Excel including 2007 SP3, 2010 SP2, 2013 SP1, 2016, and Office 2016 Click-to-Run and Mac editions. The flaw resides in how macro settings are enforced within the application, creating a security feature bypass that allows malicious actors to execute unauthorized code. The vulnerability stems from insufficient validation of macro security policies, particularly when Excel processes files that contain embedded macros or when users interact with certain file formats that may trigger macro execution without proper user consent.
The technical implementation of this vulnerability involves a weakness in the macro security enforcement mechanism where Excel fails to properly validate or enforce the configured macro security settings. This creates an opportunity for attackers to bypass the intended security controls that should prevent automatic execution of macros when documents are opened or when specific actions are performed within the application. The flaw essentially allows threat actors to circumvent the security controls designed to protect users from potentially malicious macro code execution, particularly when dealing with documents that have been crafted to exploit the bypass mechanism.
From an operational impact perspective, this vulnerability enables attackers to deliver malicious documents that can execute harmful code without user interaction or explicit consent. The attack surface is significant as it affects widely deployed versions of Microsoft Office across enterprise environments, potentially allowing for initial access, persistence, or privilege escalation within target networks. The vulnerability can be exploited through social engineering campaigns where users open malicious Excel files, or through targeted attacks that leverage the bypass to execute payload code directly within the Excel application environment. This creates a serious risk for organizations that rely on macro security controls to prevent malicious document execution.
Organizations should implement immediate mitigations including updating to the latest Microsoft Office patches and security updates that address this vulnerability. Security administrators should also enforce strict macro security policies and consider disabling macros entirely for users who do not require them for legitimate business purposes. The implementation of application control solutions and endpoint detection and response systems can help detect and prevent exploitation attempts. Additionally, user education and awareness programs should emphasize the dangers of opening unexpected Excel documents, particularly those received via email or downloaded from untrusted sources. This vulnerability aligns with CWE-693, which addresses protection mechanism failures, and maps to ATT&CK technique T1193, which covers Spearphishing Attachments, as it enables attackers to deliver malicious payloads through document-based attacks. Organizations should also consider implementing network-based protections such as email filtering and web proxies that can detect and block suspicious Office document attachments. The security feature bypass nature of this vulnerability requires comprehensive defensive measures that go beyond traditional endpoint protection to include layered security controls that can detect and prevent exploitation attempts regardless of the specific attack vector used.