CVE-2026-50428 in Windows
Summary
by MITRE • 07/14/2026
Out-of-bounds read in Windows Container Isolation FS Filter Driver (unionfs.sys) allows an authorized attacker to disclose information locally.
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Analysis
by VulDB Data Team • 07/14/2026
This vulnerability exists within the Windows Container Isolation File System Filter Driver known as unionfs.sys which is responsible for managing file operations in containerized environments. The out-of-bounds read flaw occurs when the driver processes certain file system requests without proper bounds checking on user-supplied data structures, allowing an authenticated local attacker to read memory locations beyond the intended buffer boundaries. This type of vulnerability falls under the CWE-129 weakness category which specifically addresses insufficient validation of length of input buffers, and can be categorized as a memory safety issue that enables information disclosure through improper access to kernel memory regions.
The technical implementation of this vulnerability involves the unionfs.sys driver failing to validate array indices or buffer sizes when processing file system operations within containerized workloads. An attacker with local access and appropriate privileges can craft malicious file system requests that cause the driver to read beyond allocated memory boundaries, potentially exposing sensitive kernel data including credential information, system pointers, or other confidential data structures. This weakness is particularly concerning in containerized environments where multiple isolated processes may be running on the same host system, as it could potentially enable information leakage across container boundaries.
The operational impact of this vulnerability extends beyond simple information disclosure as it creates potential pathways for further exploitation within containerized environments. Attackers could leverage this information disclosure to gather intelligence about the target system's memory layout, identify security mechanisms, or discover other vulnerabilities that might exist in the kernel components. The local nature of the attack means that the attacker must already have legitimate access to the system, but in containerized deployments where multiple users or applications share the same host, this could enable privilege escalation or lateral movement attacks. According to ATT&CK framework, this vulnerability maps to T1059.007 for Windows Command Shell and T1068 for Exploitation for Privilege Escalation, as it provides a foundation for more sophisticated attack vectors.
Mitigation strategies should focus on both immediate patching and operational security improvements. Microsoft has released security updates that address the out-of-bounds read in unionfs.sys through proper bounds checking mechanisms and input validation. Organizations should prioritize applying these patches to all affected Windows systems running containerized workloads, particularly those with multiple users or untrusted applications. Additionally, implementing least privilege access controls, disabling unnecessary container features, and employing robust monitoring solutions can help detect anomalous file system behavior that might indicate exploitation attempts. Network segmentation and container runtime security solutions should also be deployed to limit the potential impact of successful attacks, as the vulnerability could potentially be leveraged in combination with other techniques to achieve more significant compromises within containerized environments.