CVE-2026-70277 in Windows
Summary
by MITRE • 10/14/2026
Out-of-bounds read in Windows Fast FAT Driver allows an unauthorized attacker to disclose information locally.
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Analysis
by VulDB Data Team • 10/14/2026
The vulnerability identified as an out-of-bounds read within the Windows Fast Fat Driver represents a critical memory safety flaw that compromises the integrity of system data access mechanisms. The File Allocation Table, commonly referred to as FAT, is a file system architecture used in various storage devices and legacy systems, while the Fast Fat driver serves as the kernel-mode component responsible for handling these operations efficiently. When an attacker triggers this specific code path through local interaction with affected files or directories, the driver fails to properly validate memory boundaries before reading data from disk structures. This lack of rigorous bounds checking allows the system to access memory locations that lie outside the intended buffer limits, leading to a classic out-of-bounds read condition where sensitive kernel memory contents are exposed rather than just causing an immediate crash.
From a technical perspective, this flaw aligns with CWE-125, which defines Out-of-Bounds Read vulnerabilities occurring when software reads data past the end or before the beginning of the intended buffer. In the context of Windows operating systems, such errors in kernel-mode drivers are particularly severe because they operate at ring 0 privilege level. The attacker does not need to exploit a complex chain of logic bugs; instead, by crafting specific file system requests that trigger this boundary violation, they can cause the driver to leak information from adjacent memory regions. This could include pointers, stack data, or other kernel structures that were inadvertently loaded into registers or cached during the erroneous read operation. The vulnerability is strictly local in nature, meaning it requires physical access or existing user-level privileges on the target machine to initiate the exploit sequence.
The operational impact of this vulnerability centers primarily on information disclosure rather than direct code execution or denial of service, although instability remains a secondary risk if the leaked data causes subsequent logic errors within the kernel. By exploiting this flaw, an unauthorized local attacker can gather critical intelligence about the system's memory layout and running processes. This disclosed information is highly valuable for constructing further attacks, such as bypassing Data Execution Prevention (DEP) or Address Space Layout Randomization (ASLR), which are standard security mitigations designed to prevent remote code execution. The ability to read arbitrary kernel memory effectively lowers the barrier for privilege escalation attacks, allowing a low-privileged user to potentially gain higher system rights by leveraging leaked pointers and cryptographic keys stored in memory.
In terms of threat classification, this vulnerability maps directly to MITRE ATT&CK technique T1083, which covers File and Directory Discovery, although it extends beyond mere discovery into the realm of sensitive information extraction via Memory Dumping or similar techniques like T1057 if used for process observation. It also relates to T1003, specifically OS Credential Dumping, as kernel memory often contains cached credentials or security tokens that can be extracted and replayed. The vulnerability highlights a persistent challenge in legacy driver development where performance optimizations sometimes come at the cost of rigorous input validation and boundary checks.
Mitigation strategies for this issue require immediate attention to patch management protocols. Organizations should apply the latest cumulative updates provided by Microsoft, which typically include fixes for such kernel-mode vulnerabilities as part of their regular security release cycles. For environments where patching is not immediately feasible, network segmentation can help isolate systems from potential lateral movement vectors that might be enabled if an attacker successfully escalates privileges using this information leak. Additionally, enforcing strict user privilege policies and limiting local administrative rights reduces the attack surface by ensuring fewer users have the necessary permissions to interact with low-level file system drivers in a manner that could trigger such exploits. Continuous monitoring for unusual memory access patterns or kernel anomalies can also aid in detecting attempted exploitation of this flaw before significant damage occurs.