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": "2026-08-11T17:19:03.657Z",
  "pubdate": "2026-08-11T17:19:03.657Z",
  "executiveSummary": "A heap-based buffer overflow vulnerability exists within Microsoft Office Excel, potentially allowing an unauthorized local attacker to execute arbitrary code.\nThe vulnerability represents a critical security flaw in memory management operations during the parsing of malformed spreadsheet files.\nSuccessful exploitation of this flaw can lead to local code execution under the security context of the currently logged-on user, resulting in full compromise of application integrity and potential escalation of access if the user possesses elevated privileges.\nThe affected product is Microsoft Office Excel. The risk implications are severe due to the potential for arbitrary code execution upon opening a maliciously crafted document.\nAttacker capabilities are constrained by the privileges of the local user running the vulnerable application, but successful exploitation does not require prior authentication.\nExploitation requirements typically involve social engineering to trick a target user into opening a specially crafted file designed to trigger the heap corruption.",
  "technicalDetails": "The vulnerability is a heap-based buffer overflow residing in the file parsing routines of Microsoft Office Excel.\nThe root cause stems from improper boundary checking and insufficient validation of length parameters when allocating and populating heap memory buffers during the ingestion of complex spreadsheet structures.\nWhen a specially crafted Excel document containing malformed records or excessive data fields is processed, the application calculates an incorrect buffer size for heap allocation.\nSubsequent copy operations write past the boundaries of the allocated heap chunk, resulting in heap memory corruption.\nThis corruption overwrites adjacent heap metadata or critical function pointers maintained by the memory allocator.\nAn attacker crafts the payload to precisely manipulate the heap layout, ensuring that overflowed data overwrites target structures with malicious shellcode addresses.\nWhen the application attempts to dereference the corrupted pointers or execute the overwritten function handlers, control flow is hijacked and redirected to the attacker-supplied payload.\nThe vulnerable component is the internal parser responsible for handling specific record types within Microsoft Office Excel files.\nAuthentication requirements are none, and network exposure is local, as the attack vector requires the processing of a local file.\nPrivilege requirements are minimal, requiring only standard user privileges to open the malicious document.\nPost-exploitation impact includes the execution of arbitrary code, installation of malware, deployment of persistence mechanisms, and potential lateral movement within the network depending on the targeted user's privileges."
}