CVE-2026-85791

Analyzed Analyzed - Analysis Complete

Heap-based Buffer Overflow in Windows Encrypting File System

Publication date: 2026-10-13

Last updated on: 2026-10-16

Assigner: Microsoft Corporation

Description

Heap-based buffer overflow in Windows Encrypting File System (EFS) allows an authorized attacker to elevate privileges locally.

CVSS Scores

EPSS Scores

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Meta Information

Published

2026-10-13

Last Modified

2026-10-16

Generated

2026-10-19

AI Q&A

2026-10-14

EPSS Evaluated

2026-10-18

NVD

CVE-2026-85791

EUVD

EUVD-2026-99503

Affected Vendors & Products

Vendor	Product	Version / Range
microsoft	windows_server_2012	r2
microsoft	windows_server_2012	*
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_2025	to 10.0.26100.33650 (exc)
microsoft	windows_server_2022	to 10.0.20348.5761 (exc)
microsoft	windows_server_2016	to 10.0.14393.9612 (exc)
microsoft	windows_server_2019	to 10.0.17763.9376 (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-122	A heap overflow condition is a buffer overflow, where the buffer that can be overwritten is allocated in the heap portion of memory, generally meaning that the buffer was allocated using a routine such as malloc().

Attack-Flow Graph

Executive Summary

This is a heap-based buffer overflow vulnerability in Windows Encrypting File System (EFS). It allows an authorized attacker with local access to exploit the flaw and elevate their privileges on the system.

Detection Guidance

Detection of this vulnerability requires monitoring for unusual privilege escalation attempts or heap-based buffer overflows in Windows EFS. Use Windows Event Viewer to check for Event ID 4688 (new process creation) and Event ID 4672 (special privileges assigned). Run 'wevtutil qe System /q:"*[System[(EventID=4688)]]" /c:10' to check recent process creations. Also, enable Windows Defender Exploit Guard to detect heap-based overflows with 'Set-MpPreference -EnableControlledFolderAccess Enabled' and review logs with 'Get-WinEvent -LogName "Microsoft-Windows-Windows Defender/Operational" | Where-Object {$_.Id -eq 1125}'.

Impact Analysis

An attacker could 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.

Compliance Impact

This vulnerability allows local privilege escalation via a heap-based buffer overflow in Windows EFS. Such attacks could bypass access controls, potentially exposing sensitive data. For GDPR, this may lead to unauthorized data access, violating confidentiality requirements. For HIPAA, it could compromise protected health information integrity and availability.

Mitigation Strategies

Apply the latest security updates from Microsoft to patch the heap-based buffer overflow in Windows EFS. Monitor Microsoft's update guide for patches and install them as soon as available.

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