CVE-2021-42295 in Office
Summary
by MITRE • 12/15/2021
Visual Basic for Applications Information Disclosure Vulnerability
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Analysis
by VulDB Data Team • 05/19/2026
The CVE-2021-42295 vulnerability represents a critical information disclosure flaw within the Visual Basic for Applications component of Microsoft Office applications. This vulnerability specifically affects the way VBA processes and handles certain data structures, creating an avenue for unauthorized information exposure that could compromise sensitive data within affected systems. The flaw manifests in the improper handling of memory management during VBA execution, particularly when processing malformed or specially crafted input data that triggers unexpected behavior in the underlying VBA runtime environment.
The technical implementation of this vulnerability stems from insufficient input validation within the VBA engine's memory allocation and data processing mechanisms. When a malicious user crafts specific VBA code or opens a specially constructed document containing malformed VBA elements, the runtime environment fails to properly sanitize the input before processing. This inadequate sanitization allows for information leakage through memory corruption patterns that expose previously allocated memory segments containing sensitive data such as passwords, encryption keys, or other confidential information. The vulnerability operates at the intersection of memory management and code execution, creating a condition where controlled memory access can reveal data that should remain protected.
The operational impact of CVE-2021-42295 extends beyond simple information disclosure, as it can enable attackers to gather intelligence that facilitates more sophisticated attacks. An adversary who successfully exploits this vulnerability can potentially extract sensitive credentials, application data, or system information that would otherwise remain protected. This information leakage could be leveraged to conduct further attacks including privilege escalation, lateral movement, or credential theft within the targeted environment. The vulnerability's impact is particularly concerning in enterprise environments where Microsoft Office applications are widely used and where VBA macros are frequently employed for automation and business processes.
Security professionals should consider this vulnerability in the context of the broader ATT&CK framework, particularly under the information gathering and credential access phases where such information disclosure capabilities can significantly enhance an attacker's operational effectiveness. The vulnerability aligns with CWE-200, which specifically addresses "Information Exposure" and represents a classic case of improper information handling that can lead to unauthorized data access. Organizations should implement layered defensive measures including macro security policies, user education programs, and network monitoring to detect potential exploitation attempts. The recommended mitigations include disabling VBA macros in untrusted documents, implementing strict macro security settings, and ensuring timely deployment of Microsoft security updates that address this specific memory handling flaw.
This vulnerability demonstrates the persistent challenges in securing complex software environments where legacy components like VBA continue to pose security risks despite their widespread use in business applications. The flaw underscores the importance of continuous security assessment and the need for organizations to maintain comprehensive patch management programs that address both known and emerging threats within their software ecosystems.