Description

Heap-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": "2026-08-11T17:19:04.780Z",
  "pubdate": "2026-08-11T17:19:04.780Z",
  "executiveSummary": "This vulnerability involves a heap-based buffer overflow flaw present within Microsoft Office Excel. The weakness enables an unauthorized local attacker to achieve arbitrary code execution on target systems hosting the vulnerable software.\nThe primary impact of successful exploitation is complete system compromise within the context of the currently logged-on user. If the user possesses administrative privileges, the attacker gains full control over the underlying operating system.\nAffected systems include specific configurations of Microsoft Office Excel that process maliciously crafted spreadsheet files. The risk implication is severe, as weaponized documents can be distributed via common vectors such as email attachments or shared network drives.\nAttacker capabilities are constrained by the necessity to execute code locally, implying the attacker must either have pre-existing local access or trick a user into opening a specially crafted file. No complex authentication mechanisms are bypassed during the initial exploitation phase, as the attack leverages memory corruption primitives triggered during document parsing.",
  "technicalDetails": "The root cause of the vulnerability stems from insufficient bounds checking during the parsing of specific structural records within Microsoft Office Excel files. When the application encounters malformed or maliciously manipulated data fields, it allocates a dynamic memory buffer on the heap that is insufficiently sized to accommodate the incoming payload.\nThe vulnerable component resides within the core file parsing engine of Microsoft Office Excel responsible for interpreting binary or structured spreadsheet formats. The heap-based buffer overflow occurs when the application attempts to copy data into the undersized heap buffer, resulting in a contiguous memory overwrite.\nExploitation requires the victim to open a specially crafted spreadsheet file using a vulnerable version of Microsoft Office Excel. Upon parsing the malicious file, the application processes the oversized input, overflowing the heap buffer and corrupting adjacent heap metadata or critical application structures.\nBy carefully crafting the payload, an attacker can manipulate heap metadata or overwrite function pointers and virtual method tables located on the heap. When the application subsequently attempts to dereference these corrupted pointers or execute overridden structures, control flow is hijacked, allowing the execution of arbitrary shellcode contained within the payload.\nThe attack flow proceeds as follows: First, the attacker delivers the malicious file to the target system. Second, the user opens the file with Microsoft Office Excel. Third, the parsing engine encounters the malformed record and commits the heap-based buffer overflow. Fourth, execution flow is redirected to malicious instructions provided by the attacker, achieving local code execution under the privileges of the application process.\nPrivilege requirements are limited to standard user execution rights, as the vulnerability can be triggered entirely within the unprivileged security context of the running application. Network exposure is indirect, relying on social engineering or drive-by downloads to deliver the file locally, as the flaw itself is triggered via local file processing rather than direct network listeners."
}