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": "2026-08-11T17:18:05.550Z",
  "pubdate": "2026-08-11T17:18:05.550Z",
  "executiveSummary": "A critical heap-based buffer overflow vulnerability has been identified within Microsoft Office Word. This security defect enables an unauthorized, local attacker to execute arbitrary code within the context of the currently logged-in user. The flaw resides in how Microsoft Office Word processes specific document structures, leading to memory corruption when parsing malformed input data. Successful exploitation of this vulnerability compromises the confidentiality, integrity, and availability of the affected system, potentially allowing complete host takeover depending on the privileges of the targeted user. The risk implications are severe, as opening a specially crafted document can trigger the execution of malicious payloads without requiring elevated privileges. Attacker capabilities are constrained primarily by the execution context of the targeted application process. Exploitation requirements mandate that the victim opens a maliciously crafted file supplied by the adversary, meaning social engineering or auxiliary delivery mechanisms are typically required to initiate the attack vector against the local environment.",
  "technicalDetails": "The vulnerability is a classic heap-based buffer overflow stemming from improper bounds checking during the parsing of specialized file formats within Microsoft Office Word. The vulnerable component fails to adequately validate the size parameters of embedded objects or structural elements prior to allocating and copying data into dynamic heap memory buffers. When a user opens a maliciously crafted Word document, the application parses the corrupted input streams and attempts to write data exceeding the allocated heap chunk size. This results in the overwriting of adjacent heap metadata, function pointers, or critical application data structures stored on the heap. The root cause is categorized as an insufficient input validation and memory management flaw within the document parsing engine. The exploitation method relies on heap spraying or meticulous heap grooming to manipulate the layout of memory prior to the overflow, ensuring that deterministic pointers or objects are overwritten with shellcode or ROP chains. The attack flow begins when the unauthorized attacker delivers the malformed document to the local victim via removable media, local network shares, or auxiliary transfer methods. Upon the victim opening the file with Microsoft Office Word, the parsing engine encounters the malformed structural fields, triggering the heap overflow during memory allocation routines. The execution flow is subsequently hijacked when the application attempts to execute an overwritten function pointer or method table entry, redirecting control flow to attacker-supplied shellcode. Authentication requirements are non-existent, as the vulnerability can be triggered locally by an unauthenticated user processing the file. Privilege requirements are minimal, requiring only standard user rights to launch Microsoft Office Word and open the document. Network exposure is localized, as the attack vector requires local file access rather than direct remote network interaction. The payload behavior involves executing arbitrary native instructions within the security context of the user process, potentially deploying secondary implants, establishing persistence, or escalating privileges if local kernel exploits are chained subsequently. Post-exploitation impact includes unauthorized data access, execution of arbitrary system commands, and lateral movement across the local environment."
}