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": "2026-08-11T17:18:47.080Z",
  "pubdate": "2026-08-11T17:18:47.080Z",
  "executiveSummary": "This vulnerability is classified as a heap-based buffer overflow affecting Microsoft Office Word. The security flaw allows an unauthorized local attacker to achieve arbitrary code execution on the targeted system. The impact of successful exploitation includes complete compromise of the application process, potentially leading to unauthorized data access, modification, or execution under the security context of the currently logged-in user. The affected product is Microsoft Office Word. The risk implications are severe due to the potential for local code execution upon processing a maliciously crafted document. Attacker capabilities involve local exploitation vectors, meaning the threat actor must either have local access or rely on social engineering techniques to deliver a specially crafted file to the victim machine. Based on the provided context, specific exploitation requirements include the user opening the malicious file within the vulnerable application, triggering the memory corruption condition during document parsing.",
  "technicalDetails": "The technical root cause of the vulnerability stems from improper boundary checks and memory management within the heap allocation routines of Microsoft Office Word when parsing complex or malformed document structures. Specifically, when the application attempts to allocate a specific chunk size on the heap to store parsed object data, an arithmetic overflow or miscalculation of the required buffer size occurs. This results in the allocation of a heap buffer that is insufficiently sized to accommodate the incoming data stream.\nDuring the parsing phase of the document processing lifecycle, the vulnerable component reads input data from the file and writes it into the undersized heap buffer without adequately validating the length of the source data against the destination buffer capacity. Consequently, a heap-based buffer overflow is triggered, allowing out-of-bounds memory writes to overwrite adjacent heap metadata, function pointers, or critical application objects stored within the heap memory space.\nThe attack flow initiates when a victim opens a maliciously crafted document file using Microsoft Office Word. As the parsing engine processes the malformed structures, the application executes the flawed memory allocation routine. The attacker carefully crafts the payload within the document to control the data overflowing the heap buffer. By precisely manipulating the heap layout and overwriting adjacent memory structures, the attacker can hijack the control flow of the application.\nRegarding authentication and privilege requirements, the vulnerability requires no prior authentication as it is triggered locally via file processing. The attacker requires minimal privileges to deliver the payload, and exploitation executes within the security context and privilege level of the local user running Microsoft Office Word. The network exposure for this specific vector is local, relying on file delivery via removable media, network shares, email attachments, or web downloads.\nThe payload behavior involves the execution of arbitrary shellcode or malicious instructions supplied by the attacker once control flow is successfully redirected. Post-exploitation impact includes local code execution, persistence installation, data exfiltration, or lateral movement within the environment, depending on the privileges of the compromised user session and subsequent security controls."
}