CVE-2020-24557 Trend Micro Multiple Products Improper Access Control Vulnerability
Trend Micro Apex One, OfficeScan, and Worry-Free Business Security on Microsoft Windows contain an improper access control vulnerability that may allow an attacker to manipulate a particular product folder to disable the security temporarily, abuse a specific Windows function, and attain privilege escalation.
From the CISA KEV catalogue version 2026.11.06, with Cybergen analysis. Updated 6 Nov 2026.
Should You Worry?
- CISA confirmed exploitation in the wild and added it to the Known Exploited Vulnerabilities catalogue on 3 Nov 2021.
- Rated High severity (CVSS 7.8, scored by CISA).
- It has been in the catalogue for 1,829 days. Systems still unpatched now have almost certainly been scanned for it.
What It Is
A vulnerability in Trend Micro Apex One and Worry-Free Business Security 10.0 SP1 on Microsoft Windows may allow an attacker to manipulate a particular product folder to disable the security temporarily, abuse a specific Windows function and attain privilege escalation. An attacker must first obtain the ability to execute low-privileged code on the target system in order to exploit this vulnerability. Please note that version 1909 (OS Build 18363.719) of Microsoft Windows 10 mitigates hard links, but previous versions are affected.
Affected Versions
| Product | Versions |
|---|---|
| Trend Micro Trend Micro Apex One | 2009 (on premise), SaaS |
| Trend Micro Trend Micro Worry-Free Business Security | 10.0 SP1 |
From the public CVE record, as supplied by the vendor. Always confirm against the vendor advisory.
What To Do Now
- 1
Find it
Search your asset inventory and external attack surface for Trend Micro Apex One, OfficeScan, and Worry-Free Business Security. Include cloud images, appliances and anything a supplier runs for you.
Attack Surface Management - 2
- 3
Hunt for compromise
If an affected system was reachable before you patched, assume it may have been hit. Check logs, new accounts, web shells and outbound connections from the date of exposure.
Incident Response - 4
Prove it is fixed
Rescan or test the system after patching. Upgrades that fail silently and forgotten secondary instances are common.
Penetration Testing
Vendor Advisories
The Compliance Clock
General guidance, not legal advice. Your obligations depend on your sector, scope and jurisdiction.
Not Sure If You Are Exposed?
Our attack surface and vulnerability teams can check your internet-facing estate for CVE-2020-24557 and every other exploited flaw on the list.