CVE-2026-108446 in 365 Apps for Enterprise
Summary
by MITRE • 10/16/2026
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 • 10/16/2026
The vulnerability described involves a use-after-free condition within the Microsoft Office Excel application, which presents a critical security risk allowing for remote code execution via network vectors. This class of memory corruption errors occurs when software continues to use a pointer after it has been freed from dynamic memory allocation. In the context of Excel, this flaw is typically triggered by processing specially crafted files or data streams that manipulate internal object lifecycles incorrectly. When an attacker crafts input that causes the application to release a memory block but retain a reference to it, subsequent operations on that dangling pointer can lead to arbitrary code execution if the attacker controls the content written into the freed memory region.
From a technical perspective, this vulnerability aligns with Common Weakness Enumeration identifier CWE-416, which defines use-after-free as a situation where a program uses a pointer after freeing it. This misuse often results in unpredictable behavior, including application crashes or, more severely, the ability for an attacker to hijack control flow. By carefully crafting the payload that overwrites the freed memory with malicious shellcode or pointers to existing executable code within the process space, an unauthorized actor can gain the same privileges as the user running Excel. Since Microsoft Office applications are frequently used to open documents received via email or shared through network drives, this vulnerability is particularly dangerous in enterprise environments where users routinely interact with external content without sufficient isolation mechanisms.
The operational impact of this flaw is severe due to its potential for remote code execution over a network. An attacker does not need physical access to the target system; instead, they can distribute malicious Excel files through phishing emails, compromised websites, or shared file servers. When a victim opens the crafted document, the exploit triggers automatically in many configurations, especially if macro security settings are permissive or if specific features like Power Query or certain formula parsers are involved. Successful exploitation grants the attacker full control over the affected system, enabling them to install malware, steal sensitive data, pivot to other systems on the network, and establish persistent access. This transforms a simple document viewing action into a critical breach of confidentiality, integrity, and availability.
Mitigation strategies must focus on both immediate remediation and long-term architectural defenses. The primary defense is applying the latest security updates provided by Microsoft for all versions of Office Excel affected by this vulnerability. Organizations should prioritize patching endpoints that are exposed to untrusted networks or receive external documents frequently. Additionally, implementing application control policies such as AppLocker or Windows Defender Application Control can prevent unauthorized scripts from executing within Office applications. Network segmentation and strict email filtering solutions also help reduce the attack surface by blocking malicious attachments before they reach end-user devices. Regular security awareness training for employees to recognize suspicious files is equally critical in preventing initial exploitation through social engineering tactics that often accompany such vulnerabilities.