CVE-2026-108451 in Office
Summary
by MITRE • 10/16/2026
Numeric truncation error 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 involves a numeric truncation error within the core processing engine of Microsoft Office Word, specifically affecting how certain numerical values are handled during document parsing and rendering operations. This flaw stems from improper validation or conversion logic when interpreting data structures embedded within complex documents such as those containing formulas, charts, or specialized formatting elements. When an attacker crafts a malicious file with specific numeric inputs that exceed expected bounds or trigger edge-case behavior in the integer handling routines, the application fails to correctly manage memory allocation or variable assignment. This miscalculation results in a buffer overflow or heap corruption scenario where control flow is redirected due to overwritten return addresses or function pointers stored on the stack or heap. The severity of this issue lies in its potential for remote code execution without user interaction beyond opening the file, provided that automatic content processing features are enabled by default.
From a technical perspective, this vulnerability aligns with CWE-190 Integer Overflow or Wraparound and potentially CWE-787 Out-of-bounds Write depending on the specific memory corruption mechanism triggered. The truncation error likely occurs when a large numeric value is cast to a smaller data type, such as converting a 64-bit integer to a 32-bit integer without proper range checking. This leads to negative values or unexpectedly small positive numbers being used in subsequent calculations for buffer sizes or array indices. Consequently, the application may allocate insufficient memory while attempting to write larger amounts of data derived from the original malicious input. In modern exploitation techniques, this flaw can be leveraged using advanced heap spraying methods or arbitrary read-write primitives to bypass current mitigation technologies like Data Execution Prevention and Address Space Layout Randomization. The attacker constructs a specially crafted Word document that exploits these internal arithmetic errors during the parsing phase, allowing for precise memory manipulation essential for successful code execution.
The operational impact of this vulnerability is critical as it enables an unauthorized remote attacker to execute arbitrary code on the target system over a network vector. If a user opens a maliciously constructed Office Word file hosted on a website or received via email attachment, and if automatic macro execution or content rendering settings are configured per default behavior, the exploit chain can trigger silently in the background. Successful exploitation grants the attacker full control of the affected application context, which typically runs with the privileges of the logged-in user. This level of access allows for further lateral movement within a corporate network, installation of malware such as ransomware or information stealers, and complete compromise of sensitive data stored on the endpoint. The risk is exacerbated by the ubiquity of Microsoft Office in enterprise environments and the common practice of opening documents from external sources without rigorous sandboxing or isolation protocols.
Mitigation strategies must focus on both immediate patching and long-term architectural defenses. Organizations should immediately apply the latest security updates released by Microsoft to address this specific numeric truncation flaw within Word components. Beyond patching, implementing application control policies such as Windows Defender Application Control can prevent untrusted scripts from running in Office applications. Enabling Protected View for documents originating from potentially unsafe locations ensures that content is rendered in a sandboxed environment with restricted permissions, preventing direct memory access and code execution during the initial parsing phase. Additionally, disabling automatic macro execution and configuring Group Policy settings to restrict file opening from internet zones can significantly reduce the attack surface. Regular security awareness training for employees regarding phishing tactics and suspicious document handling remains essential as social engineering often serves as the primary delivery mechanism for such exploits.