CVE-2026-55027 in Office
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 out-of-bounds read flaw within Microsoft Office applications that enables unauthorized attackers to extract sensitive information from the local system. The vulnerability stems from improper input validation mechanisms within the office suite's document processing components, specifically affecting how the software handles malformed or maliciously crafted Office documents. When a user opens or processes such documents, the application attempts to access memory locations beyond the allocated buffer boundaries, potentially exposing confidential data stored in adjacent memory regions.
The technical nature of this flaw aligns with CWE-125, which categorizes out-of-bounds read vulnerabilities as weaknesses that occur when software reads data past the end of a valid buffer. This particular vulnerability manifests within Microsoft Office's document parsing engines, where insufficient bounds checking allows attackers to manipulate input data in ways that trigger memory access violations. The operational impact extends beyond simple information disclosure, as the extracted data may include sensitive credentials, temporary file contents, or other confidential information stored in memory.
Attackers can exploit this vulnerability through social engineering campaigns targeting end users with malicious Office documents delivered via email attachments, compromised websites, or removable media. The attack vector typically involves crafting specially formatted documents that trigger the out-of-bounds read condition when processed by vulnerable Office applications. This technique falls under ATT&CK tactic TA0001 (Initial Access) and technique T1193 (Spearphishing Attachment), as it leverages user interaction with malicious files to achieve unauthorized information disclosure.
The vulnerability's exploitation requires minimal privileges since it operates locally on the target system, making it particularly dangerous for environments where users have elevated permissions or access to sensitive corporate data. Microsoft Office applications such as Word, Excel, and PowerPoint are all potentially affected, with the severity depending on the specific document format and processing path triggered by the malicious input. Security researchers have noted that this vulnerability can be chained with other exploits to create more sophisticated attack scenarios.
Organizations should implement comprehensive mitigation strategies including immediate deployment of Microsoft security patches, enhanced email filtering mechanisms, and user education programs focused on identifying suspicious Office documents. Network segmentation and privileged access controls can help limit potential damage from successful exploitation attempts. The vulnerability underscores the importance of maintaining up-to-date software versions and implementing layered security approaches to protect against sophisticated attack techniques targeting common productivity applications. Regular security assessments and monitoring for anomalous network activity can help detect exploitation attempts before they result in significant data breaches.