CVE-2026-50498

What it actually does

This is a local elevation-of-privilege vulnerability in the Windows Universal Disk Format File System Driver, commonly associated with handling UDF-formatted optical media and disk images. A crafted UDF filesystem can trigger unsafe behavior in the kernel-mode driver during parsing or mounting, potentially allowing an attacker to execute code with elevated kernel/SYSTEM-level privileges. The CVSS vector indicates local exploitation, low attack complexity, no prior privileges required, and required user interaction, with high confidentiality, integrity, and availability impact if exploitation succeeds.

Why it matters to the business

Successful exploitation can turn limited local access or a user-assisted attack into full control of an affected Windows workstation or server. This can enable credential theft, security tool tampering, persistence, lateral movement, data manipulation, and service disruption. The issue affects many supported Windows desktop and server versions, including Windows 10, Windows 11, and Windows Server releases from 2012 through 2025, so exposure may be broad in mixed Windows fleets. It is not currently listed in CISA KEV and no mature exploit is reported, but because local privilege escalation vulnerabilities are commonly chained with phishing, malware execution, or remote access footholds, patching should still be prioritized.

How an attack unfolds

An attacker first needs a way to cause an affected Windows system to process attacker-controlled UDF filesystem content. This may involve convincing a user to mount or open a crafted disk image, insert crafted removable or optical media, or otherwise interact with content that causes the UDFS driver to parse the malicious filesystem. When Windows mounts or inspects the crafted UDF volume, the vulnerable kernel driver mishandles the filesystem structures. If exploitation is successful, the attacker gains elevated privileges, potentially SYSTEM-level code execution. From there, the attacker can disable defenses, dump credentials, install persistence, access sensitive data, or move laterally. No public exploit maturity is currently reported, and the CVSS user-interaction requirement means this is more likely to be used as part of a broader intrusion chain than as a standalone remote compromise.

How to fix it

Apply the Microsoft security update that addresses this vulnerability for all affected Windows versions, including Windows 10 1607, 1809, 21H2, 22H2; Windows 11 24H2, 25H2, 26H1; and Windows Server 2012, 2016, 2019, 2022, and 2025. No exact fixed build or package version was provided in the input, so use the latest applicable Windows cumulative update from Microsoft Update, WSUS, Microsoft Update Catalog, or your endpoint management platform. Prioritize endpoints and servers where users can mount disk images, access removable media, receive email attachments, browse untrusted downloads, or run interactive sessions. Where immediate patching is not possible, reduce exposure by restricting removable media and disk-image mounting, blocking untrusted ISO/UDF content at email and web gateways, limiting local interactive access on servers, enforcing least privilege, and ensuring endpoint protection can inspect mounted images and removable media.

How to confirm the fix worked

Confirm that each affected system has installed the Microsoft security update or cumulative update released to remediate this issue. Validate OS build numbers and patch compliance using Windows Update history, enterprise patch management reporting, vulnerability scanning, and direct checks of the installed UDFS driver version at C:\Windows\System32\drivers\udfs.sys. Re-scan assets after patch deployment to confirm the vulnerability no longer appears. For high-assurance validation, compare the installed udfs.sys file version and signature date against Microsoft’s patched update metadata for the relevant Windows release. Avoid using untrusted proof-of-concept code for validation; instead, use authenticated vulnerability scanners and patch inventory evidence.

Typical attack path

1. Attacker obtains local execution opportunity or prepares malicious UDF-formatted content for user-assisted delivery.
2. Attacker delivers a crafted disk image, removable media, optical media, or other content that causes Windows to parse a UDF filesystem.
3. A user or local process mounts, opens, previews, or otherwise interacts with the crafted content.
4. The Windows UDFS kernel-mode driver processes malformed filesystem metadata and triggers the vulnerability.
5. Attacker-controlled execution escapes normal user-level constraints and obtains elevated kernel or SYSTEM privileges.
6. Attacker uses the elevated privileges to dump credentials, disable security controls, persist, access protected data, or move laterally.

How to detect it

There are no public, CVE-specific exploit indicators provided, so detection should focus on suspicious activity around UDF media or disk-image handling followed by privilege-escalation behavior. Review Windows Security, System, Microsoft-Windows-Kernel-PnP, Microsoft-Windows-DriverFrameworks-UserMode, PowerShell, Sysmon, and EDR telemetry for recent mounting of removable media or disk images followed by anomalous process creation, new services, driver loads, LSASS access, credential dumping, or security control changes. Useful Windows events include Security 4688 for process creation, 4672 for special privileges assigned, 4697 or System 7045 for service installation, 1102 for audit log clearing, and Sysmon Event ID 1 for process creation, 6 for driver loaded, 7 for image loaded if enabled, 10 for process access, 11 for file creation, and 13 for registry value changes. Investigate sequences where a UDF volume or image mount is closely followed by unexpected SYSTEM-level command shells, scripting engines, service creation, scheduled tasks, antivirus exclusion changes, or credential-access tooling. Also compare timestamps around C:\Windows\System32\drivers\udfs.sys loading or filesystem mount activity with user downloads, email attachments, removable media insertion, and EDR alerts. Because no known exploit artifacts are available, treat the IOCs below as hunting pivots and exposure indicators rather than definitive compromise proof.

• C:\Windows\System32\drivers\udfs.sys
• \SystemRoot\System32\drivers\udfs.sys
• udfs.sys
• HKLM\SYSTEM\CurrentControlSet\Services\Udfs
• FileSystem\Udfs
• UDF
• Event ID 7045
• Event ID 4697
• Event ID 4688
• Event ID 4672
• Event ID 1102
• Sysmon Event ID 1
• Sysmon Event ID 6
• Sysmon Event ID 10
• Sysmon Event ID 13

What your security team should do

• Prioritize patching on interactive Windows endpoints, jump hosts, file servers, terminal servers, and systems where users can mount disk images or use removable media.
• Deploy the latest applicable Windows cumulative security updates across all affected Windows 10, Windows 11, and Windows Server versions.
• Temporarily restrict mounting of untrusted disk images and use of removable or optical media where patching is delayed.
• Harden email, web, and endpoint controls to block or quarantine untrusted ISO, IMG, UDF, and archive-delivered disk-image content.
• Monitor for suspicious privilege escalation behavior following disk-image or removable-media mount events, especially new services, driver loads, credential dumping, or security-tool tampering.
• Review endpoint detection coverage for kernel exploitation follow-on behavior, including LSASS access, unsigned driver activity, service creation, and unexpected SYSTEM shells.
• Because the vulnerability is not currently in CISA KEV and has no reported mature exploit, treat it as important but prioritize based on exposure to interactive users and removable-media workflows.