Description

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

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "7.8",
  "pubDate": "2026-08-11T17:18:52.750Z",
  "pubdate": "2026-08-11T17:18:52.750Z",
  "executiveSummary": "This vulnerability is classified as a heap-based buffer overflow affecting Microsoft Office Word. The primary security impact involves the execution of arbitrary local code, which can compromise the integrity, availability, and confidentiality of the host system. The affected product is Microsoft Office Word, specifically concerning its document parsing and memory management mechanics. The risk implications are severe, as successful exploitation enables an unauthorized local attacker to execute machine instructions within the security context of the currently logged-in user. Attacker capabilities include full code execution, potentially leading to privilege escalation, persistent system compromise, or unauthorized access to sensitive user data. Exploitation requirements involve the user opening a specially crafted malicious document file utilizing the vulnerable parsing routines present in the affected software. Given the ubiquitous nature of word processing applications in enterprise and consumer environments, unmitigated instances of this vulnerability pose a critical threat to organizational security posture, necessitating immediate defensive intervention and rigorous input validation strategies.",
  "technicalDetails": "The technical root cause of the vulnerability stems from improper bounds checking during the allocation and management of heap memory within Microsoft Office Word. When processing specific structural elements within a document, the application fails to adequately validate the size of incoming data streams prior to writing them into pre-allocated heap buffers. This discrepancy results in a heap-based buffer overflow condition, wherein data overflows the boundaries of the intended heap chunk, corrupting adjacent memory structures, function pointers, or critical heap metadata.\nThe exploitation method relies on the delivery of a maliciously crafted document file designed to manipulate the application's heap layout. Attack flow initiates when the target user opens the malformed file using Microsoft Office Word. The vulnerable component parses the malicious payload, triggering the insecure memory copy operation. By carefully orchestrating the heap layout prior to the overflow, an attacker can overwrite adjacent heap objects with controlled binary data. This overwriting technique allows the manipulation of virtual method tables or function pointers.\nAuthentication requirements are nonexistent for the initial execution vector, as the flaw is triggered locally by processing an untrusted file format rather than authenticating against a network service. Privilege requirements dictate that the attacker must have local access or the ability to deliver the malicious document to the victim via removable media, email attachments, or internal file shares. Network exposure is indirect, relying on the delivery mechanism of the file payload rather than direct network listening sockets or remote procedure call interfaces.\nPayload behavior following the successful memory corruption involves redirecting execution flow to attacker-supplied shellcode embedded within the heap. Post-exploitation impact includes the execution of arbitrary payloads with the privileges of the user running Microsoft Office Word, facilitating further lateral movement, installation of persistent backdoors, or deployment of additional secondary payloads across the compromised local environment."
}