CVE-2026-97810 in Windows
Summary
by MITRE • 10/15/2026
Heap-based buffer overflow in Windows Container Isolation FS Filter Driver (unionfs.sys) allows an authorized attacker to elevate privileges locally.
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Analysis
by VulDB Data Team • 10/15/2026
The vulnerability identified involves a heap-based buffer overflow within the Windows Container Isolation File System Filter Driver, specifically known as unionfs.sys. This driver is responsible for managing file system operations and isolation boundaries in containerized environments on Microsoft Windows operating systems. The core technical flaw stems from improper validation of input data during memory allocation or copy operations, allowing an attacker to write beyond the bounds of a heap-allocated buffer. Heap-based overflows are particularly dangerous because they can corrupt internal data structures used by the application or system kernel, leading to arbitrary code execution with elevated privileges if exploited successfully.
An authorized local attacker who has access to the container environment can leverage this flaw to escalate their privileges from standard user rights to those of a higher-privileged account, potentially even achieving SYSTEM-level control over the host machine. This privilege escalation occurs because the unionfs.sys driver operates at a high integrity level within the Windows kernel architecture. By carefully crafting malicious input that triggers the buffer overflow, an attacker can overwrite critical memory structures such as function pointers or exception handlers. When these overwritten structures are subsequently executed by the operating system, it allows the injection and execution of arbitrary shellcode in the context of the privileged driver process.
The operational impact of this vulnerability is severe, particularly for organizations utilizing Windows containers where isolation boundaries between host and guest environments must be strictly maintained. Successful exploitation compromises not only the integrity of the container but also potentially the underlying host system if escape mechanisms are triggered through the corrupted kernel state. This undermines the fundamental security model of containerization, which relies on strong separation between processes and namespaces. Attackers can use this access to install malware, exfiltrate sensitive data, or pivot further into internal networks that were previously protected by network segmentation policies relying on host integrity.
From a classification perspective, this vulnerability aligns with CWE-122: Heap-based Buffer Overflow, which describes the condition where an application writes more data to a heap buffer than it can hold. In terms of attack tactics and techniques, exploitation falls under MITRE ATT&CK technique T1068: Exploitation for Privilege Escalation, specifically involving kernel-level exploits that abuse driver vulnerabilities to gain higher access levels. The lack of proper bounds checking in the unionfs.sys component represents a classic implementation error where developer assumptions about input size or structure are not rigorously enforced before memory operations occur.
Mitigation strategies primarily involve applying vendor-supplied security patches and updates released by Microsoft for affected Windows versions. Administrators should ensure that all systems running container workloads have the latest cumulative updates installed, which typically include fixes for kernel-mode driver vulnerabilities like this one. Additionally, implementing strict least-privilege principles within container configurations can limit the potential impact if an exploit is attempted. Security teams should also monitor for unusual process creation events or privilege changes originating from system-level drivers as part of their endpoint detection and response (EDR) strategies to identify potential exploitation attempts in real-time.