CVE-2026-83709

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Heap-based Buffer Overflow in Windows NTLM

Publication date: 2026-10-13

Last updated on: 2026-10-16

Assigner: Microsoft Corporation

Description

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

CVSS Scores

EPSS Scores

Probability:
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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-2026-83709

EUVD

EUVD-2026-99960

Affected Vendors & Products

Vendor	Product	Version / Range
Microsoft	Windows	10 Version 1607 10.0.14393.0
Microsoft	Windows	10 Version 1809 10.0.17763.0
Microsoft	Windows	10 Version 21H2 10.0.19044.0
Microsoft	Windows	10 Version 22H2 10.0.19045.0
Microsoft	Windows	11 version 23H2 10.0.22631.0
Microsoft	Windows	11 Version 23H2 10.0.22631.0
Microsoft	Windows	11 Version 24H2 10.0.26100.0
Microsoft	Windows	11 Version 25H2 10.0.26200.0
Microsoft	Windows	11 version 26H1 10.0.28000.0
Microsoft	Windows	11 Version 26H2 10.0.26300.0
Microsoft	Windows	Server 2016 10.0.14393.0
Microsoft	Windows	Server 2016 (Server Core installation) 10.0.14393.0
Microsoft	Windows	Server 2019 10.0.17763.0
Microsoft	Windows	Server 2019 (Server Core installation) 10.0.17763.0
Microsoft	Windows	Server 2022 10.0.20348.0
Microsoft	Windows	Server 2025 10.0.26100.0
Microsoft	Windows	Server 2025 (Server Core installation) 10.0.26100.0

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 NTLM (NT LAN Manager) authentication protocol. An authorized attacker with local access can exploit this flaw to execute arbitrary code with elevated privileges on affected systems.

Impact Analysis

If exploited, this vulnerability allows an attacker to gain higher-level permissions on your system, potentially leading to full control over the affected machine. This could enable installation of programs, viewing or deletion of data, or creation of new accounts with administrative rights.

Compliance Impact

This vulnerability allows local privilege escalation via a heap-based buffer overflow in Windows NTLM. Such attacks could enable unauthorized access to sensitive systems or data, potentially violating confidentiality and integrity requirements under GDPR and HIPAA. Compliance may be impacted if unauthorized access leads to data breaches or unauthorized modifications of protected health or personal information.

Mitigation Strategies

Apply the latest Windows security updates from Microsoft Update immediately to patch the heap-based buffer overflow in NTLM. Monitor Microsoft's advisory for additional guidance.

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