Description

Heap-based buffer overflow in Microsoft Office Outlook allows an unauthorized attacker to execute code over a network.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "9.8",
  "pubDate": "2026-09-08T18:20:46.070Z",
  "pubdate": "2026-09-08T18:20:46.070Z",
  "executiveSummary": "This vulnerability is identified as a heap-based buffer overflow within Microsoft Office Outlook, a critical component of the Microsoft Office suite. The flaw allows a remote, unauthorized attacker to trigger memory corruption, potentially leading to arbitrary code execution on the target system.\nThe vulnerability resides in the heap management process of the application, where improper boundary checking during the processing of data allows an attacker to overwrite adjacent memory segments. Successful exploitation could grant the attacker the same privileges as the logged-in user, facilitating unauthorized access to data, lateral movement within the network, or the installation of persistent malware.\nBecause the attack can be executed over a network, the risk is significant for any enterprise environment utilizing Microsoft Outlook. Exploitation typically requires the victim to interact with a specially crafted object or file delivered via network protocols or email attachments. Given the widespread deployment of Outlook, the potential attack surface is vast, necessitating immediate attention from security operations teams.",
  "technicalDetails": "The vulnerability is characterized as a heap-based buffer overflow occurring when the Outlook client incorrectly calculates the required size of a memory buffer during the parsing of complex data structures. When the application receives specially crafted input, it fails to perform adequate bounds checking before copying the data into a heap-allocated buffer. This failure leads to a memory corruption state where the input overflows the allocated chunk, effectively corrupting adjacent objects or heap metadata.\nIn a typical attack flow, the adversary crafts a malicious payload—such as an email attachment or a malformed data structure—designed to exceed the intended buffer capacity. When Outlook parses this input, the heap overflow allows the attacker to overwrite critical data structures, such as object pointers or function pointers within the process heap. By carefully manipulating the heap layout—a technique often referred to as heap spraying—the attacker can redirect the application's execution flow to arbitrary shellcode embedded within the payload.\nThe vulnerability affects the core memory management routines of the Outlook process. Because the heap is shared memory, corruption of heap metadata can lead to unpredictable application behavior or, more commonly, controlled execution redirection. Since the process operates with the security context of the authenticated user, the attacker can execute code that bypasses standard user-mode protections. If the application is running with elevated privileges, the impact of the resulting code execution increases commensurately.\nExploitation does not require authentication from the attacker, provided they can reach the vulnerable service or deliver the malicious content to the client. The network exposure is broad, as the vulnerability can be triggered via standard delivery vectors such as email, calendar invites, or integrated document viewing features. Post-exploitation impact includes full system compromise, exfiltration of sensitive information, or the deployment of additional malicious modules that operate in the background. The lack of robust input validation in the relevant function component remains the primary root cause, allowing for a bypass of standard memory safety protections."
}