CVE-2026-55127 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 security flaw resides within the application's handling of structured document markup and memory allocation processes, specifically affecting how Word parses and processes certain elements within rich text formats. The vulnerability stems from inadequate bounds checking mechanisms when processing specially constructed data structures that exceed allocated memory boundaries in the heap memory region.
The technical implementation of this vulnerability involves an attacker crafting a malicious word processing document containing oversized or malformed data sequences that trigger memory corruption during document rendering. When Word attempts to process these crafted elements, it fails to validate input lengths properly, allowing attackers to overwrite adjacent heap memory locations with malicious code or control pointers. This memory corruption can be exploited to redirect execution flow and ultimately achieve arbitrary code execution within the context of the targeted user's session.
The operational impact of this vulnerability extends beyond simple privilege escalation as it provides attackers with persistent access to victim systems through local code execution capabilities. The attack vector typically requires social engineering to convince users to open malicious documents, making it particularly dangerous in enterprise environments where users may encounter such documents through email attachments or web downloads. Once executed, the malicious payload can establish persistence mechanisms, harvest sensitive information, or serve as a launchpad for further attacks within the network infrastructure.
Organizations should implement immediate mitigations including disabling automatic document opening features, implementing strict file type validation policies, and deploying application whitelisting solutions to prevent execution of untrusted word processing files. Microsoft recommends applying the latest security updates and patches as soon as they become available through standard update channels. Additionally, security teams should monitor network traffic for suspicious document-related activity and implement endpoint detection and response solutions that can identify anomalous behavior associated with buffer overflow exploitation attempts.
This vulnerability aligns with common weakness enumeration CWE-121 heap-based buffer overflow and maps to attack techniques described in the mitre ATT&CK framework under initial access and execution phases. The exploitability of such vulnerabilities demonstrates the critical importance of maintaining up-to-date security patches and implementing defense-in-depth strategies that combine multiple layers of protection including network segmentation, user education programs, and continuous monitoring capabilities to detect and prevent exploitation attempts before they can cause significant damage to organizational infrastructure.