Description

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

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "7.8",
  "pubDate": "2026-08-11T17:19:05.687Z",
  "pubdate": "2026-08-11T17:19:05.687Z",
  "executiveSummary": "This vulnerability is an out-of-bounds read security flaw affecting Microsoft Office Excel. The weakness enables an unauthorized local attacker to execute arbitrary code on the target system. The primary impact of successful exploitation includes potential system compromise, arbitrary code execution within the security context of the currently logged-in user, and potential unauthorized disclosure of memory contents. The affected systems are instances of Microsoft Office Excel processing malicious spreadsheet files. The risk implications are severe due to the potential for local code execution upon opening a specially crafted document. Attacker capabilities involve the ability to execute code locally, requiring user interaction in the form of opening a malicious file provided by the adversary. Exploitation requirements mandate that the victim opens a malicious Excel file locally using a vulnerable version of Microsoft Office Excel. There is no remote network vector specified, categorizing this primarily as a local attack vector requiring user deception or prior file delivery.",
  "technicalDetails": "The vulnerability is an out-of-bounds read flaw residing within the Microsoft Office Excel component responsible for parsing and processing spreadsheet file formats. The root cause stems from insufficient bounds checking when the application reads input data structures or index offsets from a file, allowing memory reads past the allocated buffer boundary. The vulnerable component is the file parsing engine of Microsoft Office Excel. The affected versions encompass those vulnerable to the described out-of-bounds read condition. Authentication requirements are none, as the attacker leverages a locally executed file format parsing mechanism. Privilege requirements are limited to standard user privileges required to run Microsoft Office Excel and open a file. Network exposure is local, meaning the attack does not require network connectivity to initiate, but rather relies on local file access or delivery via email or web download followed by local execution. The exploitation method involves crafting a malicious spreadsheet file containing manipulated structural metadata or size parameters that trick the Excel parser into reading outside authorized memory boundaries. The step-by-step attack flow proceeds as follows: First, the unauthorized attacker creates a maliciously crafted Microsoft Office Excel file designed to exploit the out-of-bounds read condition during parsing. Second, the attacker delivers this file to the target system via local means, removable media, or social engineering vectors. Third, the victim opens the malicious file using a vulnerable installation of Microsoft Office Excel. Fourth, as the application parses the malformed structures, the lack of proper boundary validation triggers an out-of-bounds memory read. Fifth, by carefully manipulating adjacent memory structures or leveraging the read primitive in conjunction with other memory corruption weaknesses, the attacker achieves arbitrary code execution. The payload behavior executes malicious instructions under the privileges of the active user session. The post-exploitation impact includes local privilege escalation attempts, persistence establishment, data exfiltration, or lateral movement within the compromised environment, depending on the constraints of the host operating system and user access controls."
}