Description

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

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "5.5",
  "pubDate": "2026-08-11T17:19:03.930Z",
  "pubdate": "2026-08-11T17:19:03.930Z",
  "executiveSummary": "An out-of-bounds read vulnerability exists in Microsoft Office Excel, which permits an unauthorized local attacker to execute information disclosure attacks.\nThe vulnerability exposes sensitive memory contents, potentially leaking critical system or user data residing in adjacent memory regions.\nAffected systems include deployments of Microsoft Office Excel processing malicious spreadsheet files.\nThe risk implication centers on unauthorized data confidentiality breaches, as memory leakage can expose cryptographic keys, internal structures, or sensitive application data.\nAttacker capabilities are restricted to local information disclosure without direct remote code execution or modification primitives, assuming standard execution constraints.\nExploitation requirements dictate that the victim must open a specially crafted malicious Excel file using a vulnerable instance of the software, enabling the parser to trigger the out-of-bounds memory read.",
  "technicalDetails": "The vulnerability is an out-of-bounds read flaw localized within the file parsing and memory handling routines of Microsoft Office Excel.\nThe root cause stems from improper bounds validation when processing specific record structures or data streams within Excel documents, where the application fails to verify that the specified length or offset matches the allocated buffer size.\nDuring the parsing phase of a malformed Excel file, the vulnerable component reads memory past the boundaries of an intended buffer due to incorrect arithmetic or missing boundary checks.\nThe exploitation method relies on supplying a crafted document containing specially manipulated metadata or size descriptors that force the parser to access memory locations outside the allocated heap or stack buffer.\nThe attack flow begins when an unauthorized local user or victim opens the malicious file via Microsoft Office Excel.\nThe affected component processes the malicious structural elements, invoking the vulnerable function that performs the out-of-bounds read operation.\nDepending on how the application handles the retrieved out-of-bounds data, the read values may be inadvertently reflected back into application logs, error messages, or memory structures accessible to the attacker, resulting in unauthorized information disclosure.\nAuthentication requirements are none regarding the file itself, though local access or a mechanism to deliver the file to the victim is required.\nPrivilege requirements are minimal for the attacker, requiring only standard user privileges to create and distribute the malicious file or trick a user into opening it.\nNetwork exposure is local, as the vulnerability manifests during the local processing of file formats rather than via a direct network listener or remote service.\nPost-exploitation impact is strictly limited to local information leakage and memory disclosure, which could potentially aid in bypassing security mitigations such as ASLR if combined with other vulnerabilities, though the standalone impact is data confidentiality loss."
}