CVE-2026-63533 in Office
Summary
by MITRE • 08/11/2026
Heap-based buffer overflow in Microsoft Office allows an unauthorized attacker to execute code locally.
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Analysis
by VulDB Data Team • 08/11/2026
A heap-based buffer overflow vulnerability exists within Microsoft Office applications that enables unauthorized attackers to execute arbitrary code on affected systems with local privileges. This critical security flaw resides in the memory management handling of Microsoft Office components, specifically within the heap allocation and data processing mechanisms used for document parsing and rendering operations. The vulnerability manifests when the application processes malformed or specially crafted input data structures that exceed allocated buffer boundaries in heap memory regions.
The technical implementation of this vulnerability follows a classic heap overflow pattern where insufficient bounds checking occurs during dynamic memory allocation operations within Microsoft Office's document processing engines. When an attacker crafts malicious Office documents containing oversized data structures or manipulated metadata fields, the application fails to validate input lengths before copying data into heap-allocated buffers. This oversight allows attackers to overwrite adjacent memory locations including function pointers, return addresses, or other critical control data structures that govern program execution flow.
From an operational perspective, successful exploitation of this vulnerability requires an attacker to first obtain local system access through social engineering tactics such as phishing emails containing malicious Office documents or by compromising legitimate user sessions. Once executed within the context of a user's session, the attacker can leverage the heap overflow to gain elevated privileges and execute malicious code with the same permissions as the compromised user account. The impact extends beyond immediate code execution to potentially enable privilege escalation attacks that could allow full system compromise.
The vulnerability aligns with CWE-121 heap-based buffer overflow classification and maps to ATT&CK technique T1059.001 for command and scripting interpreter execution. Security professionals should implement multiple layers of defense including timely patch management as provided by Microsoft security updates, application whitelisting controls, and network monitoring to detect suspicious document processing activities. Additionally, user education regarding email security practices and enabling Microsoft Office's built-in protection features such as Protected View mode can significantly reduce exploitation success rates. Organizations must also consider implementing sandboxing technologies and endpoint detection solutions that can identify anomalous behavior patterns associated with buffer overflow exploitation attempts.
The broader implications of this vulnerability highlight the persistent challenges in memory safety within complex office productivity suites where legacy code compatibility requirements often conflict with modern security hardening practices. Microsoft's ongoing efforts to improve memory safety through technologies like Control Flow Guard and Address Space Layout Randomization provide incremental protection against such vulnerabilities, though comprehensive mitigation requires coordinated patch deployment across all affected Office versions and operating system configurations.