CVE-2026-63518 in Office
Summary
by MITRE • 08/11/2026
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 • 08/11/2026
A heap-based buffer overflow vulnerability exists in Microsoft Office Word that enables unauthorized attackers to achieve local code execution through carefully crafted malicious documents. This vulnerability stems from improper input validation within the word processing application's memory management routines when handling specific file formats or document elements. The flaw occurs during the parsing of structured data within office documents, where insufficient bounds checking allows an attacker to write beyond allocated heap memory regions. Such vulnerabilities typically arise when applications fail to properly validate the size and content of user-supplied data before copying it into fixed-size buffers located in heap memory. The technical implementation involves maliciously constructed document elements that trigger memory corruption during normal document processing operations, potentially leading to arbitrary code execution with the privileges of the targeted user account.
The operational impact of this vulnerability extends beyond simple local privilege escalation as it provides attackers with a reliable mechanism for executing malicious payloads within the context of the word processing application. Attackers can leverage this weakness by delivering specially crafted office documents through various attack vectors including email attachments, compromised websites, or removable media. Once executed, the buffer overflow can overwrite critical memory structures such as return addresses, function pointers, or control data, enabling attackers to redirect program execution flow and inject their own code into the running process. This type of vulnerability aligns with common exploit patterns documented in the attack framework where initial access is achieved through social engineering or other delivery mechanisms followed by privilege escalation using known exploitation techniques.
The remediation strategy for this vulnerability requires immediate patch deployment from Microsoft as part of their regular security updates cycle, alongside comprehensive endpoint protection measures including application whitelisting and behavioral monitoring systems. Organizations should implement multi-layered defense approaches that include user education regarding suspicious document attachments, network-based filtering solutions to block malicious content at the perimeter, and regular security assessments to identify potential exploitation attempts. Security teams must also consider implementing runtime protections such as address space layout randomization and data execution prevention mechanisms to mitigate exploitation success rates even when vulnerabilities remain unpatched temporarily.
This vulnerability type maps directly to CWE-121 heap-based buffer overflow classification which represents a fundamental weakness in memory safety controls within software applications. The attack pattern aligns with techniques documented in the MITRE ATT&CK framework under the execution and privilege escalation domains, specifically targeting process injection and code execution capabilities. Microsoft's security response typically involves providing detailed guidance on vulnerability exploitation and mitigation strategies through their security bulletins and vulnerability databases, emphasizing the importance of timely patch management across enterprise environments to prevent successful exploitation attempts.