CVE-2026-55139
Summary
by MITRE • 07/14/2026
Out-of-bounds read in Microsoft Office allows an unauthorized attacker to disclose information locally.
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Analysis
by VulDB Data Team • 07/14/2026
This vulnerability represents a critical security flaw in Microsoft Office applications that enables unauthorized attackers to perform out-of-bounds read operations, potentially leading to local information disclosure. The technical implementation involves memory access violations where the application attempts to read data from memory locations outside the bounds of allocated buffers or arrays. Such flaws typically occur when input validation is insufficient or when buffer management logic fails to properly check array indices against valid memory boundaries. The vulnerability manifests when Office applications process specially crafted documents or files that contain malformed data structures designed to trigger these memory access violations.
The operational impact of this vulnerability extends beyond simple information disclosure, as it can potentially expose sensitive system data including memory contents, credential information, or other confidential data stored in adjacent memory locations. Attackers can leverage this flaw by enticing users to open malicious Office documents through various attack vectors such as email attachments, compromised websites, or social engineering campaigns. The out-of-bounds read behavior often occurs during document parsing operations when the application attempts to process corrupted or malformed file structures, particularly in complex office document formats like docx, xlsx, or pptx files that contain embedded objects or metadata.
From a cybersecurity perspective, this vulnerability aligns with CWE-125 which specifically addresses out-of-bounds read conditions in software implementations. The attack pattern follows typical exploit development methodologies where initial access is gained through phishing or delivery mechanisms, followed by privilege escalation or information harvesting from the compromised system. This flaw can be categorized under ATT&CK technique T1059 for execution and T1041 for data extraction, as attackers may use the information disclosure to gather intelligence about the target system or user environment.
Mitigation strategies should include immediate deployment of Microsoft security updates and patches that address the specific buffer overflow conditions in Office applications. Organizations must implement comprehensive email filtering systems to prevent malicious document delivery, maintain strict application whitelisting policies, and conduct regular security awareness training for users. Additionally, network segmentation and monitoring systems should be configured to detect anomalous file access patterns or memory usage behaviors that might indicate exploitation attempts. System administrators should also consider implementing exploit prevention technologies such as address space layout randomization and data execution prevention mechanisms to reduce the effectiveness of potential exploitation attempts.
The vulnerability demonstrates the ongoing challenges in securing complex office productivity suites where extensive parsing logic must handle numerous document formats while maintaining robust security boundaries. Regular security assessments, code reviews focusing on memory management practices, and adherence to secure coding guidelines are essential for preventing similar issues in future development cycles. Organizations should also maintain detailed incident response procedures specifically tailored to address exploitation attempts targeting Microsoft Office vulnerabilities, ensuring rapid containment and remediation of any successful attacks.