Description

Out-of-bounds write in Microsoft Office Excel allows an unauthorized attacker to execute code locally.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "7.8",
  "pubDate": "2026-08-11T17:19:04.643Z",
  "pubdate": "2026-08-11T17:19:04.643Z",
  "executiveSummary": "This vulnerability is classified as an out-of-bounds write flaw affecting Microsoft Office Excel.\nThe security defect allows an unauthorized local attacker to achieve arbitrary code execution on target systems.\nThe primary impact of successful exploitation includes full compromise of the application process, potentially leading to unauthorized data access, modification, or destruction within the security context of the locally logged-on user.\nThe risk implications are severe due to the prevalence of Microsoft Office Excel in enterprise environments and the potential for weaponized documents to serve as initial access vectors.\nAttacker capabilities require local access or user interaction, typically involving tricking a victim into opening a specially crafted malicious Excel file.\nExploitation requirements include the presence of the vulnerable Microsoft Office Excel software and a failure to validate boundary conditions during the parsing of specific file formats, leading to memory corruption.",
  "technicalDetails": "The root cause of the vulnerability resides in the memory management logic of Microsoft Office Excel, specifically during the parsing and processing of structural elements within spreadsheet files.\nAn out-of-bounds write occurs when the application attempts to write data past the designated boundary of an allocated buffer in memory.\nThe vulnerable component is the file parsing engine responsible for interpreting specific record types within Microsoft Office Excel.\nExploitation occurs step-by-step as follows: First, the attacker crafts a malicious Excel file containing manipulated structural metadata designed to deceive the parsing engine regarding the size and location of allocated memory buffers.\nSecond, the victim opens the malicious file using a vulnerable version of Microsoft Office Excel.\nThird, during the parsing phase, the application miscalculates the required buffer size or fails to perform adequate bounds checking prior to memory write operations.\nFourth, this failure results in heap or stack corruption as arbitrary or attacker-controlled data is written beyond the boundaries of the target buffer, overwriting adjacent memory regions, function pointers, or critical application data structures.\nFinally, by carefully controlling the layout of the corrupted memory, the attacker redirects execution flow to malicious shellcode contained within the payload, achieving code execution locally.\nAuthentication requirements: None are required within the context of opening a local file, as the vulnerability is triggered via local file processing.\nPrivilege requirements: The attacker requires standard user privileges to deliver and execute the malicious file locally on the target system.\nNetwork exposure: The vulnerability does not inherently require network exposure, as it is triggered locally, though files may be delivered via network vectors such as email attachments or shared drives.\nPost-exploitation impact includes arbitrary code execution under the privileges of the current user, enabling the deployment of secondary payloads, persistence mechanisms, and lateral movement across the internal network."
}