PT-2026-42157 · Microsoft · Defender

Acd421 + 3 · Published 2026-05-19 · Updated 2026-07-09 · CVE-2026-41091

Positive Technologies (AI Summary)

CVSS v3.1

7.8

High

Base vector

AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Name of the Vulnerable Software and Affected Versions Microsoft Defender (affected versions not specified)

Description Improper link resolution before file access, also known as link following, in the Microsoft Malware Protection Engine allows an authorized attacker to locally elevate privileges to SYSTEM level. Additionally, the Microsoft Defender Antimalware Platform contains an issue related to uncontrolled resource consumption that could allow an attacker to cause a denial of service. This flaw was actively exploited in real-world incidents before patches were released.

Recommendations Update Microsoft Defender immediately. Keep Windows fully patched. Enable multi-factor authentication and the principle of least privilege. Monitor for suspicious privilege escalation activity.

Exploit

Fix

LPE

DoS

Link Following

Resource Exhaustion

Weakness Enumeration

CWE-59

CWE-400

Related Identifiers

BDU:2026-07109

BDU:2026-07110

CVE-2026-41091

Affected Products

Defender

References · 106

• 🔥 https://github.com/0xBlackash/CVE-2026-41091 · Exploit
• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-41091 · Vendor Advisory
• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-45498 · Vendor Advisory
• https://bdu.fstec.ru/vul/2026-07109 · Security Note
• https://msrc.microsoft.com/update-guide/en-US/vulnerability/CVE-2026-41091 · Vendor Advisory
• https://nvd.nist.gov/vuln/detail/CVE-2026-41091 · Security Note
• https://bdu.fstec.ru/vul/2026-07110 · Security Note
• https://twitter.com/lyrie_ai/status/2063474531549778131 · Twitter Post
• https://i.redd.it/jur840xctp9h1.png · Reddit Post
• https://twitter.com/TheHackersNews/status/2057416212456628525 · Twitter Post
• https://twitter.com/TechTranslators/status/2057193245583515856 · Twitter Post
• https://twitter.com/PurpleOps_io/status/2057381889388826721 · Twitter Post
• https://twitter.com/NetSecIO/status/2057539610956161420 · Twitter Post
• https://twitter.com/Tajallius/status/2057645556600639773 · Twitter Post
• https://twitter.com/AseemShrey/status/2074643658398396497 · Twitter Post