CVE-2026-97016 in Outlook
Summary
by MITRE • 10/15/2026
Heap-based buffer overflow in Microsoft Office Outlook allows an unauthorized attacker to execute code over a network.
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Analysis
by VulDB Data Team • 10/15/2026
The vulnerability described constitutes a critical security flaw within the Microsoft Office Outlook application, specifically manifesting as a heap-based buffer overflow condition. This type of memory corruption error occurs when a program writes data beyond the allocated boundaries of a buffer located in the dynamic memory pool, commonly known as the heap. Unlike stack-based overflows which are often easier to exploit due to predictable memory layouts, heap-based vulnerabilities require more sophisticated exploitation techniques because the heap is shared among multiple processes and objects, making it difficult for an attacker to precisely control the flow of execution without causing a crash or triggering anti-exploitation mechanisms such as Data Execution Prevention (DEP) or Address Space Layout Randomization (ASLR). The presence of this flaw indicates that Outlook fails to adequately validate input data lengths before processing them, allowing maliciously crafted content to overwrite adjacent memory structures.
From an operational perspective, the severity of this vulnerability is significantly amplified by its network-based attack vector. An unauthorized attacker does not need physical access or local user privileges on the target machine; instead, they can exploit the flaw remotely over a network connection. This typically involves tricking a victim into opening a specially crafted email message, calendar item, or contact card that triggers the vulnerable code path within Outlook. Upon processing this malicious content, the buffer overflow condition is triggered, allowing the attacker to inject and execute arbitrary shellcode on the affected system. The potential impact includes complete compromise of the user's account, installation of malware, theft of sensitive data stored locally by Outlook such as emails and contacts, or using the compromised machine as a pivot point for further attacks within an internal network infrastructure.
This vulnerability aligns with Common Weakness Enumeration (CWE) identifier CWE-122, which describes heap-based buffer overflow conditions where memory is allocated dynamically during runtime. Furthermore, in terms of offensive security frameworks like MITRE ATT&CK, this exploit scenario maps to techniques involving remote code execution via client-side applications, often categorized under initial access vectors such as Spearphishing Attachment or Exploit Public-Facing Application if the vector involves direct network services rather than email clients alone. The exploitation relies on manipulating how Outlook parses specific data structures, highlighting a failure in input validation and boundary checking procedures within the application's codebase.
Mitigation strategies for this vulnerability primarily involve applying vendor-supplied security patches that address the underlying memory management errors. Organizations should prioritize updating Microsoft Office Outlook to versions where these heap allocation checks have been hardened against overflow conditions. In environments where immediate patching is not feasible, network-level controls such as email filtering gateways can be configured to inspect and strip potentially malicious content before it reaches end-user clients. Additionally, enforcing least-privilege principles for user accounts running Outlook reduces the impact of a successful exploitation event by limiting the permissions available to any injected code. Security awareness training remains crucial to prevent users from interacting with suspicious emails that may contain payloads designed to trigger this specific memory corruption flaw.