CVE-2026-69778 in 365 Apps for Enterprise
Summary
by MITRE • 09/09/2026
Heap-based buffer overflow in Microsoft Office Access allows an unauthorized attacker to execute code over a network.
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Analysis
by VulDB Data Team • 09/09/2026
The vulnerability described constitutes a critical security flaw within the Microsoft Office Access application, specifically manifesting as a heap-based buffer overflow condition. This type of memory corruption error occurs when a program writes more data to a dynamically allocated block of memory on the heap than it was intended to hold. In the context of Microsoft Office Access, this defect is triggered by processing specially crafted files or inputs that exceed the expected boundaries of the allocated memory space. The presence of such an overflow allows for arbitrary write operations within the process memory, which can overwrite adjacent data structures, including function pointers and exception handlers. This manipulation fundamentally compromises the integrity of the application's execution flow, providing a pathway for malicious actors to inject and execute arbitrary code with the privileges of the currently logged-in user.
From a technical perspective, heap-based buffer overflows are particularly dangerous because they do not require direct control over the stack pointer, making them harder to detect through traditional stack-smashing techniques. Instead, attackers exploit the allocator's metadata or use advanced exploitation methods such as fastbin attacks or arbitrary write primitives to gain code execution. The vulnerability is classified under CWE-122, which denotes a buffer overflow occurring in heap memory, and it aligns with MITRE ATT&CK technique T1059, specifically Command and Scripting Interpreter sub-techniques often used for initial access and lateral movement. Because the flaw resides within Office Access, a widely deployed enterprise productivity tool, the attack surface is significantly broadened compared to isolated applications.
The operational impact of this vulnerability is severe due to its network-vector capability. The ability to execute code over a network implies that an attacker does not need physical or local access to the target machine. Instead, they can deliver malicious payloads through various vectors such as email attachments, shared network drives, web-based file downloads, or instant messaging applications where Access files are commonly exchanged. Once triggered, the vulnerability allows for complete system compromise. An unauthorized attacker can install programs, view, change, or delete data, and create new accounts with full user rights. This effectively grants the adversary persistent access to the victim's environment, facilitating further stages of an attack chain such as credential harvesting, privilege escalation, and lateral movement across the corporate network.
Mitigation strategies must address both immediate remediation and long-term defensive posture. The primary defense is the timely application of security updates provided by Microsoft that patch this specific heap overflow condition in Office Access components. Organizations should prioritize deploying these patches to all endpoints running vulnerable versions of the software. Additionally, implementing strict email filtering rules to block or quarantine suspicious file attachments can reduce exposure. Network segmentation and monitoring for anomalous process creation events related to msaccess.exe can help detect exploitation attempts in real-time. Furthermore, enforcing application whitelisting policies that prevent unauthorized executables from running within Office processes adds a layer of defense-in-depth against code execution resulting from this vulnerability.