CVE-2026-108427 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 document processing engine of Microsoft Office Word, 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 dynamic memory pool, known as the heap. In the context of Microsoft Office applications, this often happens during the parsing and rendering of complex document structures or embedded objects where input validation is insufficient. When an attacker crafts a malicious Word document containing specially formatted content with oversized fields or malformed data structures, they can trigger this overflow condition. The excessive data overwrites adjacent memory locations on the heap, which may contain critical control data such as function pointers or exception handlers. This corruption allows for arbitrary code execution because the compromised program flow is redirected to execute attacker-supplied shellcode rather than legitimate application logic.
From a technical perspective, this vulnerability aligns with Common Weakness Enumeration (CWE) category CWE-122, which defines heap-based buffer overflows as writing data past the end or beginning of a heap allocated buffer. The exploitation mechanism typically involves precise memory layout manipulation to ensure that the overwritten control data points to executable code injected by the attacker. This is often achieved through techniques like Return-Oriented Programming (ROP) if direct execution is mitigated by modern security features such as Data Execution Prevention (DEP). However, given the high privilege level and complex nature of Office applications, attackers can frequently bypass these protections using advanced exploitation chains that chain multiple vulnerabilities or leverage specific application behaviors to gain control over the instruction pointer. The presence of this flaw in Word highlights the risks associated with processing untrusted content from external sources, as the application must interpret a wide variety of formatting instructions and embedded media types.
The operational impact of this vulnerability is severe due to its remote code execution capability via network vectors. An attacker does not need physical access or user interaction beyond opening the malicious document in many scenarios, although social engineering often plays a role in getting users to open crafted files. Once executed, the malware can perform any action that the compromised user account permits, including installing additional backdoors, stealing sensitive data, creating new accounts for persistent access, or joining the system to a botnet. This makes it a prime target for targeted attacks and widespread ransomware distribution campaigns. The ability to execute code over the network means that threat actors can propagate this vulnerability through email attachments, shared network drives, or web-based document repositories without requiring direct remote shell access to the host machine initially.
To mitigate the risks associated with this heap-based buffer overflow, organizations should prioritize immediate patching of Microsoft Office and Windows operating systems to apply vendor-provided security updates that address the memory management flaws in the Word rendering engine. Administrators should enforce strict application control policies using tools like AppLocker or Windows Defender Application Control to restrict the execution of untrusted scripts and binaries from temporary directories where downloaded documents are often saved. Additionally, enabling Protected View for all Office files opened from potentially unsafe locations can sandbox the document processing, preventing malicious code from executing within the main process space. Users should be educated on phishing awareness to avoid opening attachments from unknown sources, as technical controls alone cannot fully eliminate social engineering risks. Regular vulnerability scanning and monitoring of endpoint detection systems for anomalous behavior patterns associated with exploitation attempts are also recommended defense-in-depth strategies. This incident underscores the importance of maintaining up-to-date software configurations and employing layered security measures to protect against memory corruption vulnerabilities that remain a prevalent threat in enterprise environments.