Description

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

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "7.8",
  "pubDate": "2026-08-11T17:18:46.073Z",
  "pubdate": "2026-08-11T17:18:46.073Z",
  "executiveSummary": "This vulnerability is classified as a heap-based buffer overflow affecting Microsoft Office. The security flaw presents a critical risk to system integrity and confidentiality, allowing an unauthorized local attacker to achieve arbitrary code execution within the context of the user running the vulnerable application.\nThe vulnerability arises during the processing of specially crafted data structures by Microsoft Office, leading to memory corruption on the heap. If successfully exploited, an attacker can manipulate heap metadata or overwrite adjacent memory regions with malicious payloads, bypassing standard security controls.\nExploitation requires the local execution of untrusted files or interaction with malicious document inputs, meaning attackers must rely on social engineering or prior local access to deliver the malicious payload. Successful code execution grants the attacker the execution privileges of the targeted user, potentially leading to complete system compromise, data exfiltration, or the deployment of secondary malware payloads.\nOrganizations utilizing affected versions of Microsoft Office must prioritize remediation through official vendor updates and implement defense-in-depth measures to restrict the execution of untrusted documents and mitigate potential local privilege escalation scenarios.",
  "technicalDetails": "The vulnerability is a heap-based buffer overflow residing within the memory management routines of Microsoft Office when parsing malformed file formats. The root cause stems from insufficient bounds checking and improper validation of size parameters prior to allocating and copying data into dynamic heap buffers.\nWhen a user opens a malicious file constructed to exploit this flaw, the vulnerable component attempts to read structured data into a fixed-size heap buffer without adequately validating the length of the input stream. This discrepancy between the allocated buffer size and the incoming data volume results in a heap overflow condition.\nDuring exploitation, the overflow corrupts adjacent heap chunks, metadata pointers, or virtual function tables residing on the heap. By carefully crafting the input data, an attacker can manipulate the heap layout to achieve deterministic memory corruption. When the application subsequently interacts with the corrupted pointers or structures, execution control is hijacked, allowing the processor to execute attacker-supplied shellcode.\nThe attack flow proceeds as follows: First, the unauthorized attacker crafts a malicious document designed to trigger the heap-based buffer overflow. Second, the file is delivered to the target system via local transfer, removable media, or social engineering vectors. Third, the local user opens the file using the vulnerable Microsoft Office application. Fourth, the application parses the malformed structures, initiating the out-of-bounds write on the heap. Finally, memory corruption occurs, leading to arbitrary local code execution under the security context of the logged-on user.\nThe vulnerable component involves internal parsing functions responsible for handling complex object layouts within Microsoft Office documents. Authentication is not required for the initial trigger beyond local access to open the file, and the privilege level required to execute the exploit is restricted to standard user privileges, aligning with the operational permissions of the targeted application."
}