CVE-2026-97761 in Office
Summary
by MITRE • 10/15/2026
Stack-based buffer overflow in Microsoft Office Excel allows an unauthorized attacker to execute code over a network.
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Analysis
by VulDB Data Team • 10/15/2026
The vulnerability described constitutes a critical security flaw within the Microsoft Office Excel application, specifically manifesting as a stack-based buffer overflow condition. This type of memory corruption error arises when a program writes more data to a fixed-length block of memory on the call stack than it is allocated to hold. In the context of Excel, this typically occurs during the processing of specially crafted files or documents that contain malformed input vectors designed to exploit specific parsing routines. When an attacker crafts a malicious file with oversized fields or improperly structured data structures, they can overwrite adjacent memory locations on the stack, including critical control flow information such as return addresses and saved frame pointers. This overwriting allows for arbitrary code execution by redirecting the program's instruction pointer to shellcode injected into the buffer itself or to existing executable modules within the application environment.
From a technical perspective, this vulnerability aligns with Common Weakness Enumeration identifier CWE-121, which defines stack-based buffer overflow as a memory corruption flaw where data is written beyond the bounds of a fixed-size buffer on the call stack. The exploitation mechanism relies heavily on precise control over the input stream to ensure that the overwritten return address points to executable code within the process space. Modern operating systems employ various mitigations such as Data Execution Prevention and Address Space Layout Randomization, which can complicate direct exploitation; however, attackers often utilize techniques like Return Oriented Programming or heap spraying to bypass these protections if they are not fully configured or updated. The presence of this flaw indicates a failure in input validation and bounds checking within the Excel rendering engine or file parser components responsible for handling specific document formats or embedded objects.
The operational impact of successfully exploiting this vulnerability is severe, granting an unauthorized attacker full control over the affected system under the context of the currently logged-in user. This level of access enables the installation of malware, the theft of sensitive data stored locally on the machine, and the use of the compromised host as a pivot point for further attacks within a networked environment. Since Microsoft Office applications are ubiquitous in enterprise environments, this vulnerability presents a significant risk vector for phishing campaigns or drive-by download attacks where users might be tricked into opening maliciously crafted Excel files via email attachments or shared drives. The ability to execute code remotely means that no physical access is required, making it particularly dangerous against distributed workforces and organizations with high volumes of external document exchange.
To mitigate the risks associated with this vulnerability, immediate patching through Microsoft Security Updates is paramount. Organizations should ensure that all endpoints running affected versions of Excel are updated to the latest stable release containing the fix for this specific flaw. In addition to software updates, defense-in-depth strategies should be employed, including enabling Enhanced Security Configuration in Office applications to restrict macro execution and limit access to external content. Network segmentation can also help contain potential lateral movement if a host is compromised. Furthermore, user awareness training regarding phishing tactics and suspicious file attachments remains a critical layer of defense against social engineering attempts that seek to deliver the exploit payload. Regular vulnerability scanning and monitoring for anomalous process behavior related to Office applications can aid in early detection of exploitation attempts before significant damage occurs.