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": "2026-08-11T17:19:05.953Z",
  "pubdate": "2026-08-11T17:19:05.953Z",
  "executiveSummary": "A stack-based buffer overflow vulnerability has been identified within Microsoft Office Excel. This security flaw enables an unauthorized, local attacker to achieve arbitrary code execution on target systems processing maliciously crafted spreadsheet files. The vulnerability resides in the application's parsing logic when handling specific file structures, failing to adequately bound input data copied into fixed-size stack buffers. Successful exploitation compromises the confidentiality, integrity, and availability of the host system, potentially leading to full user session takeover depending on the privilege level of the interacting user. Risk implications are severe, as Microsoft Office formats are commonly processed across enterprise environments via email attachments or shared network drives. Exploitation requires the victim to open a specially crafted file using the vulnerable application. No authentication or elevated privileges are required by the attacker prior to file delivery, though local access or user interaction in the form of opening the malicious document is necessary to trigger the flaw.",
  "technicalDetails": "The vulnerability is a classic stack-based buffer overflow stemming from unsafe memory handling operations during the parsing of malformed records within Microsoft Office Excel files. Specifically, the vulnerable component lacks proper bounds checking mechanisms when reading input streams into stack-allocated buffers. When a user opens a maliciously crafted spreadsheet, the application parses the structural records of the file. If an attacker manipulates specific length specifiers or record headers within the file format, the internal parsing routines copy data exceeding the destination buffer's allocated capacity onto the call stack. This results in the overwriting of adjacent stack memory, including critical execution control data such as the saved frame pointer and the return address. Upon completion of the vulnerable function, the corrupted return address is loaded into the instruction pointer, redirecting execution flow to attacker-controlled shellcode or a payload engineered via Return-Oriented Programming gadget chains. The attack vector requires local delivery or user interaction, typically manifested by convincing a target to open a malicious document via email or web download. Because the vulnerability triggers during document parsing, it requires no authentication and executes within the security context of the locally logged-in user running Microsoft Office Excel. Post-exploitation impact includes the execution of arbitrary commands with the privileges of the victim user, facilitating lateral movement, data exfiltration, or the installation of persistent malware within the host environment."
}