CVE-2026-83949 in Office
Summary
by MITRE • 09/09/2026
Buffer over-read in Microsoft Office Word allows an unauthorized attacker to disclose information locally.
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Analysis
by VulDB Data Team • 09/09/2026
The vulnerability identified as a buffer over-read within Microsoft Office Word represents a critical memory safety flaw that compromises the confidentiality of data processed by the application. This specific type of error occurs when software reads beyond the allocated boundaries of a buffer, accessing adjacent memory locations that were not intended to be accessed. In the context of Microsoft Office Word, this defect allows an unauthorized attacker who has local access to the system to exploit the flaw and disclose sensitive information stored in the process memory space. The nature of a buffer over-read is distinct from more destructive vulnerabilities like buffer overflows because it typically does not allow for arbitrary code execution or immediate denial of service through stack corruption; instead, its primary impact lies in the unauthorized leakage of data that resides immediately following the targeted buffer in memory.
From a technical perspective, this vulnerability stems from improper validation of input parameters or insufficient bounds checking during the processing of specific document structures or embedded objects within Word documents. When an attacker crafts a malicious file containing specially constructed content designed to trigger the flawed logic, they can cause the application to read data outside its designated buffer limits. This action results in the exposure of internal memory contents which may include sensitive user information such as credentials, encryption keys, session tokens, or other proprietary data held by the operating system and running applications. The exploitation requires local access because the attacker must be able to execute code on the target machine that interacts with Microsoft Office Word, typically by tricking a privileged user into opening a malicious document or through automated scripts if execution policies are permissive.
The operational impact of this vulnerability is primarily centered around information disclosure rather than system compromise in terms of control. While it does not directly grant an attacker remote code execution capabilities, the ability to read arbitrary memory locations can serve as a powerful stepping stone for further attacks. For instance, disclosed memory contents might reveal security tokens or passwords that could be used to escalate privileges or move laterally within a network environment if those credentials are reused across systems. Furthermore, in multi-tenant environments or shared workstations, this vulnerability poses a significant risk to data privacy and compliance with regulations such as GDPR or HIPAA, which mandate strict controls over the handling of sensitive personal information. The existence of such flaws undermines trust in the integrity of office productivity suites used extensively in enterprise settings for critical business operations.
To mitigate the risks associated with this buffer over-read vulnerability, organizations should prioritize applying the latest security patches released by Microsoft as part of their regular update cycles. These updates typically include code changes that enforce stricter memory access controls and improve input validation mechanisms within Word processing engines. Additionally, implementing application whitelisting can prevent unauthorized or untrusted scripts from executing malicious documents automatically without user interaction. Security awareness training is also crucial to ensure employees recognize the risks associated with opening files from unknown sources. For environments where high security is paramount, deploying advanced endpoint protection solutions that monitor for anomalous memory access patterns can provide an additional layer of defense against exploitation attempts targeting this class of vulnerabilities.
In terms of industry standard classifications, this vulnerability aligns with CWE-125 Out-of-bounds Read, which describes the scenario where software reads data past the end or before the beginning of the intended buffer. This classification highlights the fundamental memory safety error involved in the flaw. Furthermore, from a tactical perspective related to adversary behavior, exploitation techniques for such vulnerabilities often fall under ATT&CK technique T1005 Data from Local System which covers scenarios where attackers retrieve sensitive data directly from local systems without necessarily compromising them fully. Understanding these mappings helps security teams align their detection and response strategies with established frameworks designed to identify and mitigate similar memory corruption issues across various software platforms.