CVE-2026-80085 in Office
Summary
by MITRE • 09/09/2026
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 • 09/09/2026
The vulnerability described constitutes a critical security flaw within the Microsoft Office Word application, 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 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. The attacker constructs input data designed to exceed the expected size limits of internal buffers used for handling document elements such as images, embedded objects, or complex formatting structures. When Word attempts to process these malformed inputs, it fails to perform adequate bounds checking, resulting in adjacent memory being overwritten with malicious code or shellcode.
The operational impact of this vulnerability is severe due to its potential for remote code execution over a network. Because Microsoft Office applications are widely used and often configured to automatically open documents from email attachments or shared drives without extensive user intervention, the attack vector is highly accessible. An unauthorized attacker can distribute a malicious document via phishing emails, file sharing services, or compromised websites. Upon opening the crafted file, the vulnerability allows for arbitrary code execution with the privileges of the current user. This means that if an administrator opens such a document, the attacker gains administrative control over the system. Even for standard users, successful exploitation can lead to complete compromise of the workstation, including data theft, installation of malware, or use as a pivot point for further lateral movement within the corporate network.
From a technical classification perspective, this vulnerability aligns with CWE-120, which denotes Buffer Copy without Checking Size of Input, and more specifically CWE-787, Out-of-bounds Write in the heap space. The exploitation technique often involves manipulating data structures to overwrite function pointers or exception handling records on the stack or heap, thereby redirecting program execution flow to attacker-controlled code. In terms of adversary tactics, this aligns with MITRE ATT&CK techniques related to Initial Access via Spearphishing Attachment and Execution through Command and Scripting Interpreter, as well as Defense Evasion mechanisms that may be employed by malware delivered through such exploits to hide from security solutions. The heap-based nature of the overflow makes it particularly dangerous because modern operating systems employ various memory protection mechanisms like Data Execution Prevention (DEP) and Address Space Layout Randomization (ASLR). However, sophisticated exploit developers often use techniques such as Return-Oriented Programming (ROP) or information leakage to bypass these protections, making successful exploitation feasible even on patched or hardened systems if the specific vulnerability is present.
Mitigation strategies must focus on both immediate remediation and long-term defense in depth. The primary corrective action is the timely application of security updates provided by Microsoft that address this heap overflow issue within Word's parsing libraries. Organizations should ensure their patch management processes are agile enough to deploy these fixes rapidly across all endpoints. Additionally, implementing Application Control policies can prevent untrusted scripts or binaries from running after exploitation occurs. Network segmentation and strict email filtering rules that inspect attachments for known malicious patterns or suspicious file types also reduce the attack surface. User awareness training is equally critical; employees should be educated to recognize social engineering attempts and avoid opening documents from unknown sources, even if they appear legitimate. Finally, enabling macro security settings to disable macros by default in Office applications can mitigate risks associated with document-based attacks that rely on embedded scripts for post-exploitation activities.