CVE-2026-108426 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 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 structures. This overwrite mechanism allows an unauthorized remote attacker to gain arbitrary code execution capabilities on a targeted system by manipulating the program flow and redirecting instruction pointers to shellcode embedded within the overflowed buffer.
From a technical perspective, heap-based vulnerabilities are particularly dangerous because they can often be exploited without direct user interaction beyond opening or viewing the malicious file, depending on the specific configuration of the Office application and its macro security settings. The operational impact is severe, as successful exploitation grants the attacker full control over the affected system under the context of the current user privileges. This level of access enables a wide range of destructive activities including data theft, installation of backdoors for persistent remote access, deployment of ransomware, or using the compromised machine as part of a larger botnet infrastructure. The network-based nature of this vulnerability means that it can be propagated via email attachments, shared network drives, or web-hosted documents, significantly increasing the attack surface and potential blast radius across an enterprise environment.
This specific flaw aligns with Common Weakness Enumeration identifier CWE-122, which defines heap-based buffer overflow as a weakness where data is written beyond the bounds of a dynamically allocated memory block. Furthermore, in terms of tactical classification within the MITRE ATT&CK framework, this vulnerability facilitates initial access through exploited remote services or malicious files (T1566) and potentially leads to privilege escalation if the user account has elevated permissions. The exploitation chain typically involves crafting a malformed document that triggers the overflow during parsing, followed by memory corruption techniques such as heap spraying or use-after-free scenarios to achieve reliable code execution.
Mitigation strategies must focus on both technical controls and administrative policies. Organizations should immediately apply vendor-provided security patches and updates for Microsoft Office products to address the underlying buffer handling logic flaws. Network segmentation can help limit lateral movement if a single endpoint is compromised, while strict email filtering rules that block executable attachments or macro-enabled documents from external sources reduce exposure. Additionally, enabling Enhanced Security Configuration in Office applications restricts active content execution by default, and deploying application whitelisting solutions prevents unauthorized binaries from running even if the initial exploit succeeds. Regular vulnerability scanning and penetration testing should be conducted to identify unpatched instances of this software within the infrastructure, ensuring that remediation efforts are prioritized based on risk exposure.