CVE-2026-55140
Summary
by MITRE • 07/14/2026
Heap-based buffer overflow in Microsoft Office allows an unauthorized attacker to execute code locally.
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Analysis
by VulDB Data Team • 07/14/2026
A heap-based buffer overflow vulnerability exists within Microsoft Office applications that enables unauthorized attackers to execute arbitrary code on a target system with local privileges. This critical security flaw resides in the memory management implementation of office suite components, specifically affecting how the software handles dynamic memory allocation and data processing within heap memory structures. The vulnerability manifests when maliciously crafted Office documents are opened, triggering improper memory handling that leads to buffer overflow conditions in heap-allocated memory regions.
The technical exploitation of this vulnerability occurs through carefully constructed input data that exceeds the allocated buffer boundaries within heap memory segments. When Microsoft Office processes these malformed inputs, the software fails to properly validate or sanitize the data before copying it into insufficiently sized heap buffers. This results in memory corruption that can be leveraged by attackers to overwrite adjacent memory locations, potentially including return addresses, function pointers, or other critical control data structures. The heap-based nature of this vulnerability makes it particularly challenging to detect and exploit compared to stack-based counterparts due to the more complex memory allocation patterns and less predictable memory layout.
From an operational perspective, successful exploitation of this vulnerability allows attackers to achieve local code execution with the privileges of the targeted user account. This can lead to complete system compromise, data exfiltration, persistence mechanisms establishment, or lateral movement within network environments. The attack vector typically involves social engineering campaigns where users are tricked into opening malicious Office documents through email attachments, compromised websites, or removable media. Once executed, the attacker gains the ability to install additional malware, modify system configurations, access sensitive files, or establish backdoor access points for continued unauthorized access.
Organizations should implement multiple layers of defense to mitigate this vulnerability effectively. Immediate remediation includes applying official Microsoft security updates and patches that address the heap buffer overflow conditions in affected Office components. System administrators should also deploy application whitelisting solutions such as Windows Defender Application Control or similar technologies to restrict execution of unauthorized code. Network segmentation and monitoring controls should be enhanced to detect anomalous behavior patterns associated with exploitation attempts, including unusual memory allocation activities or process injection behaviors. Regular security awareness training for end users helps reduce successful social engineering attacks that often precede exploitation of such vulnerabilities.
This vulnerability aligns with CWE-121 heap-based buffer overflow classification and maps to several ATT&CK techniques including T1059 command and control, T1068 local privilege escalation, and T1547 account manipulation. The attack surface extends across multiple Microsoft Office applications including Word, Excel, PowerPoint, and Outlook, making comprehensive patch management essential for organizational security posture. Security professionals should monitor advisories from Microsoft and cybersecurity vendors to stay informed about related exploitation techniques and emerging threat intelligence surrounding this vulnerability type.
The root cause of this vulnerability stems from inadequate input validation and memory management practices within Microsoft Office's document processing engines. Development teams should follow secure coding guidelines that emphasize proper bounds checking, memory allocation verification, and defensive programming techniques to prevent similar issues in future releases. Regular code reviews and automated static analysis tools can help identify potential heap overflow conditions before they reach production environments. Additionally, implementing runtime protections such as address space layout randomization, data execution prevention, and heap corruption detection mechanisms provides additional defense-in-depth measures against exploitation attempts.
Organizations must also consider the broader implications of this vulnerability within their overall security framework, including incident response procedures for detecting and containing exploitation attempts. Regular penetration testing and vulnerability assessments should include evaluation of Office document processing capabilities to identify potential memory corruption scenarios. The remediation process requires coordination between IT operations, security teams, and business stakeholders to ensure timely patch deployment while minimizing operational disruption. Continuous monitoring of system logs, network traffic, and endpoint behaviors remains crucial for early detection of exploitation attempts that may bypass initial security controls.