CVE-2026-55130 in Office
Summary
by MITRE • 07/14/2026
Heap-based buffer overflow in Microsoft Office Word allows an unauthorized attacker to execute code locally.
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Analysis
by VulDB Data Team • 07/15/2026
A heap-based buffer overflow vulnerability exists in Microsoft Office Word that enables remote code execution when a maliciously crafted document is opened by an unsuspecting user. This critical flaw resides in the way Word processes certain elements within document files, specifically when handling memory allocation for heap-based data structures during document parsing operations. The vulnerability stems from insufficient bounds checking mechanisms that fail to validate the size of data being written to heap-allocated memory regions, allowing attackers to overwrite adjacent memory locations with malicious code payloads.
The technical implementation of this vulnerability involves the manipulation of Word's document processing engine to trigger memory corruption through carefully crafted input data. When a user opens an affected Word document, the application attempts to parse and render specific elements such as tables, headers, footers, or embedded objects that contain oversized or malformed data structures. The heap allocation routines do not properly validate incoming data lengths against allocated buffer sizes, creating opportunities for attackers to overflow memory boundaries and potentially overwrite critical execution pointers or return addresses within the process heap.
This vulnerability presents significant operational risks as it requires minimal user interaction beyond opening a malicious document, making it particularly dangerous in targeted attack scenarios. The attack vector typically involves spearphishing campaigns where attackers send carefully crafted Word documents to specific individuals or organizations. Once executed, the malicious code can establish persistence mechanisms, exfiltrate data, or provide remote access capabilities to threat actors. The vulnerability affects multiple versions of Microsoft Office Word across different operating systems and is particularly concerning due to its local execution nature which bypasses many network-based security controls.
From a cybersecurity maturity perspective, this vulnerability aligns with CWE-121 heap-based buffer overflow category and maps to multiple ATT&CK techniques including initial access through spearphishing, execution via office applications, and privilege escalation mechanisms. Organizations should implement immediate mitigations including applying Microsoft security patches, deploying application control policies that restrict Word from opening untrusted documents, and implementing email filtering measures to block suspicious attachments. Network segmentation and endpoint detection systems should be enhanced to monitor for anomalous behavior patterns associated with document processing activities, while regular security awareness training can help reduce successful social engineering attempts targeting this vulnerability class.
The exploitation of such vulnerabilities demonstrates the persistent challenge organizations face in defending against sophisticated attacks targeting widely used productivity applications. Microsoft's security response typically involves releasing patches that address memory management flaws within their software libraries, but organizations must maintain proactive defense measures including regular vulnerability assessments, penetration testing focused on document processing components, and maintaining updated threat intelligence feeds to identify emerging attack patterns targeting similar vulnerabilities.