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": "2026-08-11T17:18:47.223Z",
  "pubdate": "2026-08-11T17:18:47.223Z",
  "executiveSummary": "A heap-based buffer overflow vulnerability exists within Microsoft Office, specifically impacting how the software processes designated data structures. This vulnerability permits an unauthorized local attacker to execute arbitrary code within the security context of the currently logged-in user.\nThe flaw introduces significant risk to organizational endpoints utilizing affected Microsoft Office versions. Successful exploitation compromises the confidentiality, integrity, and availability of the host system. Depending on the privileges held by the user executing the vulnerable application, an attacker could inherit administrative rights, facilitating full system compromise, lateral movement across the network, and the deployment of persistent malware payloads.\nAttacker capabilities are constrained primarily by local execution requirements, necessitating that the threat actor either has direct interactive access to the target machine or can deliver a specially crafted file to be processed by the victim. The attack vector relies on memory corruption primitives to manipulate heap metadata, ultimately hijacking the application execution flow.\nMitigation requires applying vendor-supplied security updates as soon as they become available, enforcing the principle of least privilege for user accounts, and implementing robust endpoint detection mechanisms to monitor for anomalous process behavior and memory manipulation attempts.",
  "technicalDetails": "The vulnerability is classified as a heap-based buffer overflow, stemming from improper bounds checking during the parsing of specific file formats within Microsoft Office. The vulnerable component fails to adequately validate the size of incoming data prior to copying it into a dynamically allocated heap buffer, leading to memory corruption.\nRoot cause analysis indicates that when Microsoft Office parses malformed input data, the application allocates a fixed-size buffer on the heap but subsequently writes a variable length of data that exceeds the allocated boundary. This results in the overwriting of adjacent heap chunks, including critical metadata structures such as chunk headers, pointers, or function pointers utilized by the runtime environment.\nExploitation occurs step-by-step as follows: First, the attacker crafts a malicious file containing oversized data payloads designed to target the vulnerable heap allocation routines. Second, the victim opens the crafted file using the affected Microsoft Office application. Third, the application parses the malformed structures, triggering the buffer overflow condition as excessive data is written past the designated heap boundary. Fourth, the attacker carefully engineers the overflow to overwrite adjacent memory pointers with controlled values. Finally, when the application attempts to dereference the corrupted pointers or execute hijacked function pointers, the execution flow is redirected to attacker-supplied shellcode or Return-Oriented Programming (ROP) chains.\nAuthentication requirements are minimal to none from a network perspective, as the attack vector is local; however, successful execution depends on local user interaction to open the malicious file. The privilege requirements are limited to standard user rights, matching the integrity level of the targeted Microsoft Office process. Network exposure is typically indirect, relying on social engineering or email delivery mechanisms to place the malicious file onto the local file system. Post-exploitation impact includes arbitrary code execution, privilege escalation if auxiliary vulnerabilities or weak configurations are present, and installation of persistent backdoors."
}