Description

Stack-based buffer overflow in Microsoft Office Excel allows an unauthorized attacker to execute code locally.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "7.8",
  "pubDate": "2026-08-11T17:19:06.080Z",
  "pubdate": "2026-08-11T17:19:06.080Z",
  "executiveSummary": "A stack-based buffer overflow vulnerability has been identified within Microsoft Office Excel. This security flaw permits an unauthorized attacker to achieve local code execution on target systems hosting the vulnerable software. The core risk centers on memory corruption, which can be leveraged by malicious actors to compromise system integrity and execute arbitrary commands under the security context of the currently logged-in user. The vulnerability impacts Microsoft Office Excel environments and requires local interaction, typically involving the victim opening a maliciously crafted spreadsheet file designed to trigger the stack-based memory overwrite. Successful exploitation bypasses standard security controls inherent to the application architecture, potentially leading to a full system compromise depending on user privileges. Mitigation requires applying official vendor patches and adhering to strict file-handling security policies for untrusted documents.",
  "technicalDetails": "The vulnerability is classified as a stack-based buffer overflow residing within the file-parsing components of Microsoft Office Excel. The root cause stems from insufficient bounds checking when the application processes specially crafted record structures within Excel documents. Specifically, when the vulnerable component attempts to read untrusted input data into a fixed-length stack buffer, it fails to validate the size of the incoming data against the allocated memory space.\nThe attack flow begins when an unauthorized attacker delivers a maliciously modified Excel file to the victim via local storage, removable media, or social engineering vectors. Upon opening the file, the parsing engine reads the oversized data structure and writes it sequentially onto the stack without enforcing rigorous length restrictions. This causes adjacent stack memory, including saved frame pointers and return addresses, to be overwritten with attacker-controlled data.\nWhen the affected function attempts to return execution flow, the corrupted return address points to malicious shellcode injected into the stack by the payload. Consequently, the CPU instruction pointer is redirected to execute the arbitrary payload. Exploitation requires local access and user interaction to open the file, but does not necessitate prior authentication. The network exposure is strictly local, though combined with other vectors or secondary payloads, it can facilitate broader system infiltration. The post-exploitation impact includes arbitrary code execution with the privileges of the target user, enabling unauthorized data access, persistence installation, and lateral movement within the local environment."
}