CVE-2026-83857

Analyzed Analyzed - Analysis Complete

Use-After-Free in Windows UDFs Driver Enables Local Privilege Escalation

Publication date: 2026-10-13

Last updated on: 2026-10-21

Assigner: Microsoft Corporation

Description

Use after free in Windows Universal Disk Format File System Driver (UDFS) allows an authorized attacker to elevate privileges locally.

CVSS Scores

EPSS Scores

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Meta Information

Published

2026-10-13

Last Modified

2026-10-21

Generated

2026-11-08

AI Q&A

2026-10-14

EPSS Evaluated

2026-11-07

NVD

CVE-2026-83857

EUVD

EUVD-2026-100016

Affected Vendors & Products

Vendor	Product	Version / Range
microsoft	windows_server_2012	r2
microsoft	windows_server_2012	*
microsoft	windows_server_2022	to 10.0.20348.5761 (exc)
microsoft	windows_10_1607	to 10.0.14393.9612 (exc)
microsoft	windows_10_1607	to 10.0.14393.9612 (exc)
microsoft	windows_10_1809	to 10.0.17763.9376 (exc)
microsoft	windows_10_1809	to 10.0.17763.9376 (exc)
microsoft	windows_10_21h2	to 10.0.19044.7807 (exc)
microsoft	windows_10_21h2	to 10.0.19044.7807 (exc)
microsoft	windows_10_21h2	to 10.0.19044.7807 (exc)
microsoft	windows_11_23h2	to 10.0.22631.7652 (exc)
microsoft	windows_11_23h2	to 10.0.22631.7652 (exc)
microsoft	windows_11_24h2	to 10.0.26100.9711 (exc)
microsoft	windows_11_24h2	to 10.0.26100.9711 (exc)
microsoft	windows_11_25h2	to 10.0.26200.9711 (exc)
microsoft	windows_11_25h2	to 10.0.26200.9711 (exc)
microsoft	windows_11_26h1	to 10.0.28000.3231 (exc)
microsoft	windows_11_26h1	to 10.0.28000.3231 (exc)
microsoft	windows_11_26h2	to 10.0.26300.9711 (exc)
microsoft	windows_11_26h2	to 10.0.26300.9711 (exc)
microsoft	windows_server_2016	to 10.0.14393.9612 (exc)
microsoft	windows_server_2019	to 10.0.17763.9376 (exc)
microsoft	windows_server_2025	to 10.0.26100.33650 (exc)
microsoft	windows_10_22h2	to 10.0.19045.7807 (exc)
microsoft	windows_10_22h2	to 10.0.19045.7807 (exc)
microsoft	windows_10_22h2	to 10.0.19045.7807 (exc)

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-121	A stack-based buffer overflow condition is a condition where the buffer being overwritten is allocated on the stack (i.e., is a local variable or, rarely, a parameter to a function).

Attack-Flow Graph

Executive Summary

This vulnerability is a use-after-free issue in the Windows Universal Disk Format File System Driver (UDFS). It allows an authorized attacker to elevate their privileges locally on affected systems.

Detection Guidance

Detection typically requires monitoring for unusual privilege escalation attempts or crashes in the UDFS driver. Check Windows Event Logs for application or system crashes related to udfs.sys. Use PowerShell commands like Get-WinEvent -LogName System | Where-Object {$_.Message -like "*udfs.sys*"} to filter relevant events.

Impact Analysis

An attacker could exploit this to gain higher-level permissions on your system, potentially allowing them to install programs, view or delete data, or create new accounts with full user rights.

Mitigation Strategies

Apply the latest Windows security updates from Microsoft Update immediately. Disable the UDFS driver if not needed via Device Manager or Group Policy. Monitor Microsoft's advisory page for patches and additional guidance.

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