CVE-2026-108430 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.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
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. This type of memory corruption error occurs when a program writes data beyond the allocated boundaries of a buffer located in the heap segment of computer memory. In the context of Microsoft Office Word, this defect is typically triggered by processing specially crafted documents or files that exploit parsing logic errors within the application's rendering engine or document structure handlers. The attacker constructs input data designed to exceed the expected size limits defined for specific internal buffers, thereby overwriting adjacent memory locations with malicious code or control flow redirection instructions.
From a technical perspective, heap-based buffer overflows are particularly dangerous because they allow an unauthorized actor to manipulate the program's execution state without direct user interaction beyond opening the file. When the overflow occurs, it can corrupt critical data structures such as function pointers, exception handlers, or other metadata stored in nearby memory regions. By carefully crafting the payload, a sophisticated attacker can achieve arbitrary code execution on the victim's system with the privileges of the currently logged-in user. This capability transforms what might otherwise be a simple document viewing action into a severe compromise vector, enabling full control over the affected workstation.
The operational impact of this vulnerability is significant due to its potential for remote exploitation via network vectors. Since Microsoft Office Word is widely used in enterprise and personal environments, an attacker can distribute malicious documents through email attachments, shared drives, or web downloads. Upon opening the compromised file, the application processes the malformed input, triggering the overflow condition automatically. This leads to a complete system compromise where attackers can install backdoors, steal sensitive data, deploy ransomware, or use the machine as part of a botnet for further attacks against other network resources. The ease of exploitation and high impact make this one of the most severe categories of vulnerabilities in productivity software suites.
Industry standards classify this flaw under CWE-120, which denotes Buffer Copy without Checking Size of Input, specifically highlighting the lack of proper bounds checking during memory operations. Furthermore, from a tactical standpoint aligned with MITRE ATT&CK frameworks, this vulnerability facilitates initial access through spearphishing attachment techniques and enables privilege escalation if the application runs with elevated permissions. The exploitation chain often involves bypassing security mitigations such as Data Execution Prevention (DEP) and Address Space Layout Randomization (ASLR), although modern versions of Office include enhanced protections that may raise the difficulty level for successful exploitation.
Mitigation strategies primarily involve applying vendor-supplied patches to update Microsoft Office Word to a version where the buffer handling logic has been corrected to validate input sizes strictly before allocation or copy operations. Organizations should enforce strict email filtering policies to block suspicious attachments and disable macro execution by default unless explicitly required for trusted business processes. Additionally, implementing application whitelisting can prevent unauthorized executables from running even if exploitation succeeds. Regular security awareness training for end-users remains crucial to reduce the likelihood of opening untrusted documents, serving as a vital layer of defense alongside technical controls.