CVE-2026-85909 in Windows
Summary
by MITRE • 10/14/2026
Out-of-bounds read in Windows Universal Disk Format File System Driver (UDFS) allows an authorized attacker to disclose information locally.
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Analysis
by VulDB Data Team • 10/14/2026
The vulnerability identified involves a critical out-of-bounds read flaw within the Windows Universal Disk Format file system driver, commonly referred to as UDFS.sys. This component is responsible for managing files and directories on optical discs formatted with the Universal Disk Format standard, which is widely used for DVD-ROMs and Blu-ray media. The core technical deficiency lies in how the driver processes specific input parameters or data structures associated with these disk formats without adequately validating memory boundaries. When an attacker interacts with a maliciously crafted UDFS volume or triggers a specific sequence of file system operations, the driver attempts to access memory locations that lie outside the allocated buffer space. This improper boundary check results in the reading of arbitrary kernel-mode memory contents rather than returning a controlled error code or handling the invalid input gracefully.
From an operational perspective, this vulnerability allows for local information disclosure by authorized users who have sufficient privileges to interact with the file system driver. While the impact is generally considered less severe than remote code execution vulnerabilities because it requires physical access or prior authentication on the target machine, the consequences can still be significant in high-security environments. By exploiting this out-of-bounds read, an attacker can potentially leak sensitive data from adjacent memory regions within the kernel address space. This leaked information may include cryptographic keys, session tokens, internal system structures, or other confidential data that could facilitate further attacks such as privilege escalation or bypassing security controls like Data Execution Prevention (DEP) and Address Space Layout Randomization (ASLR).
This flaw is categorized under CWE-125, which defines out-of-bounds read vulnerabilities. In the context of the MITRE ATT&CK framework, this vulnerability aligns with techniques related to Tactic TA0006, Credential Access, specifically sub-techniques involving memory scraping or data exfiltration from local processes and kernel space. It also relates to reconnaissance activities where an attacker gathers information about the system's internal state to plan subsequent exploitation steps. The nature of this vulnerability highlights the importance of rigorous input validation in low-level drivers that operate with high privileges within the operating system core.
Mitigation strategies primarily involve applying the security updates provided by Microsoft, which patch the underlying code logic to ensure proper bounds checking before memory access occurs. System administrators should prioritize installing these patches on all systems where UDFS support is enabled or required for optical media operations. Additionally, restricting physical access to machines and enforcing strict user privilege policies can reduce the attack surface available to potential exploiters. For environments with heightened security requirements, disabling unnecessary file system drivers that are not actively used may further minimize risk vectors associated with kernel-mode vulnerabilities.