CVE-2026-87699

Analyzed Analyzed - Analysis Complete

Heap-based Buffer Overflow in Winlogon

Publication date: 2026-10-13

Last updated on: 2026-10-27

Assigner: Microsoft Corporation

Description

Heap-based buffer overflow in Winlogon allows an authorized attacker to elevate privileges locally.

CVSS Scores

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Meta Information

Published

2026-10-13

Last Modified

2026-10-27

Generated

2026-11-08

AI Q&A

2026-10-14

EPSS Evaluated

2026-11-07

NVD

CVE-2026-87699

EUVD

EUVD-2026-100070

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 Winlogon, a critical Windows component. An authorized attacker can exploit it to cause a buffer overflow, potentially allowing them to elevate their privileges on the system.

Detection Guidance

Detection typically involves monitoring for unusual Winlogon.exe behavior or memory corruption patterns. Use Windows Event Viewer to check for application crashes or errors related to Winlogon. Microsoft Defender for Endpoint can also detect heap-based buffer overflows in Winlogon. Run 'sfc /scannow' to check system file integrity and 'dism /online /cleanup-image /restorehealth' to repair corrupted files.

Impact Analysis

An attacker with local access could exploit this to gain higher privileges, 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 Winlogon. Such unauthorized privilege elevation could lead to unauthorized access to sensitive data or system functions, potentially violating compliance requirements under GDPR (data protection) or HIPAA (health information security) by enabling unauthorized data access or modification.

Mitigation Strategies

Apply the latest security updates from Microsoft to patch the heap-based buffer overflow in Winlogon. Monitor Microsoft's update guide for patches and install them promptly.

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