CVE-2026-108428 in Office
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 condition that can be exploited remotely via a network connection. This type of vulnerability arises when a program writes more data to a dynamically allocated memory block on the heap than it was intended to hold, leading to adjacent memory being overwritten with potentially malicious content. In the context of Microsoft Office Word, this flaw is typically triggered by processing specially crafted documents or files that contain malformed structures within their internal formats, such as Open XML or legacy binary file types. When an attacker sends a network request containing a payload designed to exploit this overflow, they can manipulate the heap metadata and overwrite critical pointers or function addresses stored in memory.
From a technical perspective, heap-based buffer overflows are particularly dangerous because modern operating systems employ various mitigation techniques such as Address Space Layout Randomization (ASLR) and Data Execution Prevention (DEP). However, skilled attackers often use advanced exploitation techniques like Return-Oriented Programming to bypass these protections by chaining together small snippets of existing code within the application's memory space. By carefully controlling the overflow data, an attacker can redirect the execution flow of the Word process to arbitrary shellcode injected into the heap. This allows for the complete compromise of the affected system, granting the unauthorized actor full control over the operating environment without requiring any prior authentication or user interaction beyond opening a malicious file received via email or network share.
The operational impact of this vulnerability is severe due to its remote code execution capability and potential for automated exploitation through social engineering vectors like phishing campaigns. An attacker can distribute malicious documents that, upon being opened by a victim using the vulnerable version of Word, silently execute arbitrary commands on the host machine. This could lead to the installation of malware, establishment of persistent backdoors, exfiltration of sensitive corporate data, or use of the compromised system as part of a larger botnet for distributed denial-of-service attacks. The network-based nature of the attack vector means that it does not require physical access and can be propagated rapidly across organizational boundaries if email gateways fail to filter out malicious attachments effectively.
To mitigate this risk, organizations must ensure that all instances of Microsoft Office Word are updated with the latest security patches released by Microsoft addressing this specific heap overflow issue. It is also advisable to implement application control policies such as Windows Defender Application Control or AppLocker to restrict the execution of untrusted scripts and binaries from temporary folders where downloaded attachments often reside. Additionally, enabling Protected View for files originating from the internet can isolate potentially malicious documents in a sandboxed environment, preventing them from interacting with the underlying operating system until explicitly trusted by the user. Regular vulnerability scanning and penetration testing should be conducted to identify any remaining unpatched systems within the network infrastructure that remain susceptible to this exploit chain.
This vulnerability aligns closely with Common Weakness Enumeration identifier CWE-120, which classifies buffer copies without checking size limits as a fundamental software design flaw. Furthermore, in terms of adversary tactics and techniques, exploitation of this flaw maps directly to MITRE ATT&CK technique T1203, known as Exploitation for Client Execution, where attackers leverage vulnerabilities in client-side applications to gain initial access. Understanding these mappings helps security teams prioritize remediation efforts based on standardized frameworks that reflect real-world attack behaviors. Continuous monitoring of endpoint detection and response systems for anomalous process creation events following document opening can also aid in detecting active exploitation attempts before significant damage occurs.