CVE-2026-88076 in Windows
Summary
by MITRE • 10/14/2026
Null pointer dereference in Windows Installer allows an authorized attacker to elevate privileges locally.
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Analysis
by VulDB Data Team • 10/14/2026
The vulnerability described involves a null pointer dereception within the Microsoft Windows Installer service, commonly known as MSIEXEC or Windows Installer Service. This component is responsible for installing, maintaining, and removing software installations on Windows operating systems. While typically associated with system administration tasks due to its elevated privileges, it also serves as an attack surface when processing maliciously crafted installation packages. The core technical flaw lies in the failure of the installer engine to properly validate pointers before dereferencing them during specific operations involving package parsing or transformation scripts. When a specially constructed Windows Installer database is processed, certain code paths may attempt to access memory addresses that have not been initialized or are explicitly set to null. In standard programming practices, accessing a null pointer results in an immediate crash of the application due to protection faults enforced by the operating system's memory management unit. However, in this specific context within Windows Installer, the lack of adequate error handling and boundary checks allows the execution flow to continue into unintended code paths or potentially manipulate control flow structures such as function pointers or virtual table entries if the null value is interpreted incorrectly by subsequent logic blocks.
From a privilege escalation perspective, because the Windows Installer service operates with high-level system privileges, any successful exploitation of this flaw can lead to arbitrary code execution within that privileged context. An authorized attacker who has local access to the machine and sufficient permissions to trigger installation processes or interact with MSI files can craft a malicious package designed to exploit this null pointer dereference. By carefully structuring the payload, the attacker may be able to redirect program control flow to execute shellcode injected into memory. This effectively allows the attacker to bypass standard user-level restrictions and gain SYSTEM-level access, which is equivalent to full administrative control over the compromised host. The impact extends beyond simple denial of service; while a crash might occur in some scenarios, the primary concern for security professionals is the potential for remote code execution or local privilege escalation depending on how the vulnerability manifests during runtime.
This type of flaw aligns with Common Weakness Enumeration category CWE-476, which defines null pointer dereference as a weakness where a program uses a pointer that it expects to refer to valid memory but actually refers to no location in memory. The exploitation technique often involves manipulating data structures within the MSI file format, such as custom actions or script tables, to trigger the specific code path containing the defect. In terms of adversary tactics and techniques, this vulnerability supports ATT&CK T1059 Command and Scripting Interpreter for initial execution if scripts are involved, but more critically it facilitates ATT&CK T1068 Exploitation for Privilege Escalation. Attackers may use tools like Metasploit or custom-built exploit code to automate the creation of malicious MSI files that trigger this condition. The operational impact includes complete compromise of system integrity, confidentiality, and availability. Once SYSTEM access is achieved, attackers can install rootkits, modify security policies, exfiltrate sensitive data, or pivot to other systems within a network environment.
Mitigation strategies primarily rely on applying the relevant patches released by Microsoft that address this specific issue in Windows Installer components. Organizations should ensure that all endpoints are updated with the latest cumulative updates and security fixes provided through Windows Update or WSUS. Additionally, implementing strict application whitelisting policies can prevent unauthorized MSI files from being executed even if they contain exploitable code. Restricting write access to directories where installation packages might be staged reduces the risk of an attacker placing a malicious file in a location accessible by the installer service. Furthermore, monitoring for unusual activity related to Windows Installer processes, such as unexpected spawning of cmd.exe or powershell.exe from msiexec.exe, can aid in early detection and response. Security teams should also consider disabling unnecessary features within the installer if they are not required for business operations, thereby reducing the attack surface available to potential adversaries seeking to leverage this vulnerability for local privilege escalation.