CVE-2026-108429 in 365 Apps for Enterprise
Summary
by MITRE • 10/16/2026
Heap-based buffer overflow in Microsoft Office Word allows an unauthorized attacker to execute code over a network.
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Analysis
by VulDB Data Team • 10/16/2026
The vulnerability described constitutes a critical security flaw within the Microsoft Office Word application, specifically manifesting as a heap-based buffer overflow. This type of memory corruption error occurs when a program writes data beyond the allocated boundaries of a buffer located in the computer's random access memory, known as the heap. In the context of Microsoft Office Word, this defect is typically triggered by processing specially crafted documents or files that contain malformed content structures. When an attacker constructs a malicious file with precisely calculated payload sizes and offsets, they can overwrite adjacent memory locations on the heap. This overwriting capability allows for arbitrary code execution because the attacker can manipulate function pointers or exception handling mechanisms within the application's memory space to redirect program flow toward their injected shellcode.
The operational impact of this vulnerability is severe due to its potential for remote exploitation without user interaction beyond opening a malicious document, which aligns with common attack vectors in social engineering scenarios. An unauthorized attacker who successfully exploits this flaw can execute arbitrary code on the affected system under the context of the current user privileges. This means that if a standard user opens the compromised file, the attacker gains control over that user's environment, potentially leading to data theft, installation of malware, or further lateral movement within a corporate network. The ability to execute code remotely makes this vulnerability particularly dangerous in enterprise environments where employees frequently receive documents from external sources via email or shared drives.
From a technical classification perspective, this issue maps directly to Common Weakness Enumeration identifier CWE-120, which denotes Buffer Copy without Checking Size of Input. This category highlights the failure of the application to validate input data length before copying it into a fixed-size buffer. Furthermore, in terms of tactical behavior within an attack lifecycle, exploitation of this vulnerability aligns with MITRE ATT&CK techniques related to Initial Access and Execution. Specifically, attackers often leverage such vulnerabilities through Spearphishing Attachment campaigns where malicious documents are delivered via email, or they may be embedded in files hosted on compromised websites accessed by victims. The heap-based nature of the overflow suggests that exploitation requires sophisticated payload construction to bypass modern memory protection mechanisms like Data Execution Prevention and Address Space Layout Randomization, although successful exploits often include techniques to defeat these mitigations through information disclosure or specific gadget chains.
Mitigation strategies for this vulnerability primarily involve applying the latest security updates provided by Microsoft, which patch the underlying code defect responsible for the buffer overflow. Organizations should enforce strict policies regarding the opening of documents from untrusted sources and utilize application whitelisting or controlled folder access to prevent unauthorized executables from running in Office directories. Additionally, enabling Protected View for files originating from the internet can isolate potentially malicious content in a sandboxed environment, preventing direct interaction with system resources. Regular patch management is essential as these vulnerabilities are frequently targeted by automated worm-like malware that scans networks for unpatched systems. Security teams should also monitor network traffic for anomalies indicative of exploitation attempts and ensure that endpoint detection and response solutions are configured to detect suspicious memory access patterns associated with heap overflow exploits.