CVE-2026-69619 in Windows
Summary
by MITRE • 09/09/2026
Out-of-bounds read in Windows exFAT File System allows an authorized attacker to elevate privileges over a network.
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Analysis
by VulDB Data Team • 09/09/2026
The vulnerability identified as an out-of-bounds read within the Microsoft Windows exFAT file system represents a critical security flaw that can be exploited by authenticated attackers to achieve privilege escalation via network-based interactions. This specific defect resides in the core components responsible for parsing and processing metadata associated with files stored on volumes formatted using the extended File Allocation Table (exFAT) format, which is commonly used for removable media such as USB flash drives and SD cards due to its support for large file sizes and efficient space utilization compared to older FAT32 implementations. When a user or system component interacts with an exFAT volume over a network share, the operating system's kernel-mode drivers process various directory entries and allocation tables to locate files and manage storage resources. The flaw arises when these drivers fail to adequately validate the bounds of data structures during parsing operations, specifically allowing access to memory regions that lie outside the intended buffer boundaries defined by the file structure specifications.
From a technical perspective, this out-of-bounds read condition is classified under CWE-125, which denotes Out-of-Bounds Read vulnerabilities where software reads past the end or before the beginning of the intended buffer. In the context of Windows kernel operations, such memory access violations do not typically result in immediate system crashes if handled improperly by exception handlers, but rather allow an attacker to leak sensitive information from adjacent memory locations into user-space accessible buffers. This leakage can reveal critical internal state data, including pointers to other objects within the kernel address space, security tokens, or cryptographic keys stored in volatile memory. The ability to read arbitrary kernel memory provides the foundational intelligence required for subsequent exploitation steps, particularly when combined with other vulnerabilities that allow for write operations or code execution primitives.
The operational impact of this vulnerability is severe due to its potential for remote privilege escalation over a network vector. Although the attacker must initially possess valid credentials on the target system, which aligns with the requirement for an authorized user, the ability to escalate privileges from a standard user account to SYSTEM level effectively neutralizes many perimeter defenses and access control mechanisms. Once elevated privileges are obtained, the attacker gains unrestricted access to all files, registry keys, services, and security policies on the compromised host. This can lead to complete system compromise, enabling the installation of persistent backdoors, lateral movement across the network using stolen credentials or harvested hashes, and exfiltration of sensitive corporate data. The network aspect implies that if an attacker has authenticated access to a shared folder hosted on an affected Windows machine formatted with exFAT, they may exploit this flaw without needing physical proximity to the hardware.
This vulnerability maps directly to several tactics within the MITRE ATT&CK framework, most notably Initial Access through Valid Accounts and Privilege Escalation via Exploitation for Privilege Escalation. The exploitation path typically involves crafting a malicious exFAT volume or manipulating existing file structures on such a volume to trigger the out-of-bounds read condition during directory enumeration or file access operations performed by the SMB server service, which handles network file sharing requests. By carefully constructing the input data sent over the network share connection, an attacker can control what memory contents are returned in response to their queries, thereby facilitating information disclosure that aids in further exploitation stages such as heap spraying or kernel address space layout randomization bypasses.
Mitigation strategies for this vulnerability primarily involve applying the latest security updates provided by Microsoft, which patch the underlying buffer validation logic within the exFAT driver modules. Organizations should ensure that all Windows systems exposed to network shares are fully patched and up-to-date with cumulative security rollups. Additionally, administrators can reduce the attack surface by disabling unnecessary file sharing services or restricting access to shared folders containing removable media drives if such usage is not strictly required for business operations. Implementing strict input validation policies on any custom applications that interact directly with exFAT volumes via API calls can also help prevent exploitation attempts from application-layer software. Regular auditing of system logs for unusual SMB activity and monitoring for anomalies in memory access patterns using endpoint detection and response tools can aid in the early identification of potential exploitation attempts targeting this specific kernel flaw.