CVE-2026-97771 in Office
Summary
by MITRE • 10/14/2026
Use after free in Microsoft Office Excel allows an unauthorized attacker to execute code over a network.
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Analysis
by VulDB Data Team • 10/14/2026
The vulnerability described constitutes a critical security flaw within the Microsoft Office Excel application, specifically involving a use-after-free error that can be exploited by an unauthorized actor to achieve remote code execution. This type of defect arises from improper memory management practices where the software continues to reference a memory block after it has been freed or deallocated. In the context of network-based attacks, this typically occurs when an attacker crafts a malicious Excel file containing specially designed content that triggers the application to release certain resources while retaining pointers to them. When the application subsequently attempts to access these dangling pointers during normal processing operations such as rendering formulas, parsing data structures, or handling embedded objects, it interacts with memory locations that may have been reallocated for other purposes or are no longer valid. This interaction allows an attacker to manipulate the program flow and inject arbitrary shellcode into the process space of Excel, thereby gaining the ability to execute commands on the victim's system under the context of the currently logged-in user.
From a technical perspective, this vulnerability aligns with Common Weakness Enumeration identifier CWE-416 which defines use-after-free conditions as situations where pointers are used after they have been freed leading to unpredictable behavior and potential security breaches. The exploitation vector is particularly dangerous because it leverages social engineering tactics often combined with automated delivery mechanisms via email or network shares, fitting the ATT&CK technique T1205.008 known as Exploitation for Remote Code Execution through Drive-by Client-side Scripts or similar client-side exploit kits that target office applications. The impact of successful exploitation is severe as it grants the attacker full control over the affected system without requiring any additional authentication beyond opening the malicious document. This can lead to data exfiltration, installation of persistent backdoors, lateral movement within a corporate network, and complete compromise of sensitive information stored on or accessible from the compromised host.
Mitigation strategies for this vulnerability require a multi-layered approach focusing on both technical controls and user awareness. Organizations should immediately apply the latest security patches released by Microsoft to update Excel and related Office components, ensuring that memory management routines are corrected at the source level. Additionally, implementing application control policies such as AppLocker or Windows Defender Application Control can prevent untrusted scripts from running within office applications. Network segmentation and strict firewall rules limiting inbound traffic to file sharing services reduce the attack surface for network-based delivery methods. Users must be educated on recognizing suspicious attachments and avoiding opening files from unknown sources. Furthermore, enabling Protected View in Excel provides a sandboxed environment that restricts macro execution and limits access to system resources when opening documents downloaded from the internet or received via email, significantly reducing the likelihood of successful exploitation even if a malicious file is opened.