CVE-2023-33162 in Excel
Summary
by MITRE • 07/11/2023
Microsoft Excel Information Disclosure Vulnerability
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Analysis
by VulDB Data Team • 05/09/2026
Microsoft Excel contains an information disclosure vulnerability that arises from improper handling of certain file formats during the parsing process. This flaw allows attackers to potentially extract sensitive data from malformed or specially crafted Excel files through the application's processing mechanisms. The vulnerability manifests when Excel attempts to parse corrupted or maliciously constructed spreadsheet files, leading to unintended data exposure through memory contents or internal application states. The issue stems from insufficient validation of input file structures and inadequate error handling during the parsing of complex spreadsheet elements such as formulas, cell references, or embedded objects. This vulnerability falls under the CWE-200 category of "Information Exposure" and can be exploited through various attack vectors including social engineering campaigns where users open malicious files. The operational impact extends beyond simple data leakage as it can potentially enable further exploitation paths including privilege escalation or lateral movement within compromised environments. Security researchers have identified that the vulnerability is particularly pronounced when Excel processes files with malformed structured references or when handling certain types of embedded objects that trigger memory corruption states.
The technical implementation of this information disclosure vulnerability occurs at the file parsing layer within Excel's spreadsheet engine where the application fails to properly sanitize input data before processing. When encountering malformed cell references or corrupted formula structures, the application's internal memory management routines may expose sensitive information from adjacent memory locations or internal data structures. This occurs because the parsing logic does not adequately validate the bounds of memory allocations or properly isolate different data processing contexts during file interpretation. The vulnerability can be triggered through various file formats including xlsx, xlsm, and xls files that contain specially crafted elements designed to cause the application to behave unexpectedly. Attackers can leverage this flaw by constructing malicious Excel files that, when opened by victims, cause Excel to leak information from its memory space through various mechanisms including stack contents, heap data, or internal application state information. This type of vulnerability aligns with ATT&CK technique T1059.005 for "Command and Scripting Interpreter: Visual Basic" and T1566.001 for "Phishing: Spearphishing Attachment" when used in targeted attack campaigns.
Organizations affected by this vulnerability should implement immediate mitigations including restricting Excel file processing in high-security environments, deploying application whitelisting policies, and ensuring timely patching of affected systems. The recommended approach involves configuring Excel to disable automatic execution of macros and implementing strict file validation procedures for incoming spreadsheet files. Security teams should also consider deploying network-based intrusion detection systems that can identify suspicious file patterns associated with known exploit payloads. Additional protective measures include implementing user education programs to reduce the risk of social engineering attacks that rely on opening malicious Excel attachments. The vulnerability demonstrates the importance of proper input validation and memory management practices in office applications, particularly those handling complex file formats with extensive parsing requirements. Organizations should conduct regular security assessments of their spreadsheet processing environments and implement monitoring solutions that can detect anomalous behavior patterns associated with information disclosure attempts. Furthermore, maintaining up-to-date security patches and implementing defense-in-depth strategies that include multiple layers of protection will significantly reduce the attack surface and potential impact of exploitation attempts targeting this vulnerability.