Description

Heap-based buffer overflow in Microsoft Office Word allows an unauthorized attacker to execute code over a network.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "9.8",
  "pubDate": "2026-09-08T18:20:46.200Z",
  "pubdate": "2026-09-08T18:20:46.200Z",
  "executiveSummary": "A critical heap-based buffer overflow vulnerability exists within Microsoft Office Word, facilitating unauthorized remote code execution (RCE).\nThis vulnerability is categorized as a memory corruption flaw, specifically affecting the dynamic heap memory management processes when handling malformed document structures.\nThe vulnerability allows an unauthenticated, remote attacker to trigger memory corruption by enticing a user to open a specially crafted malicious document or interact with an attacker-controlled network resource.\nSuccessful exploitation grants the adversary the ability to execute arbitrary code within the security context of the currently logged-in user, potentially leading to a full system compromise, unauthorized data access, and the installation of persistent malicious payloads.\nThe risk is considered critical, as it bypasses standard application-level security controls and leverages the inherent trust placed in office document parsers.\nExploitation does not require prior authentication, and the attack vector is network-based, meaning it can be delivered via email attachments, malicious web links, or file-sharing platforms.",
  "technicalDetails": "The root cause of this vulnerability lies in the improper validation of memory allocation sizes or data bounds during the parsing of complex data structures within the Microsoft Office Word memory management subsystem.\nWhen the application processes an object containing specifically crafted metadata—typically within document headers or embedded object definitions—it may allocate an insufficient amount of heap memory for the subsequent data processing routine.\nBecause the input length is not strictly validated against the actual heap buffer size, a subsequent copy operation causes data to overflow the allocated boundaries, overwriting adjacent memory objects on the heap.\nThe exploitation flow typically involves an attacker deploying a malicious document that includes a carefully crafted heap layout. By manipulating the heap state—a technique often referred to as 'heap spraying' or 'heap grooming'—the attacker ensures that a critical target object, such as a function pointer, an object pointer, or a Virtual Method Table (vtable), is placed immediately following the overflowed buffer.\nOnce the overflow occurs, the attacker overwrites the targeted pointer with a memory address that points to their own malicious payload, often hosted in a controlled region of memory such as a heap-allocated buffer or a pre-positioned ROP (Return-Oriented Programming) chain.\nFollowing the initial memory corruption, the application is forced to reference the corrupted pointer during its normal execution flow. This redirects the CPU's instruction pointer (EIP/RIP) to the attacker-supplied shellcode or ROP gadget chain.\nExecution of the payload occurs under the privileges of the user running the Microsoft Office Word process. In environments where the user is an administrator, the attacker may gain full system control. If the user is running with restricted privileges, the attacker may subsequently utilize local privilege escalation techniques to gain elevated access.\nThis vulnerability is particularly dangerous as it circumvents standard memory safety mechanisms. The attack flow is silent, often requiring minimal user interaction beyond simply opening a file, making it a high-utility vector for targeted campaigns."
}