Improper Access Control in Trend Micro Apex One, OfficeScan, and Worry‑Free Business Security (CVE‑2020‑24557) Enables Privilege Escalation
What It Is – Trend Micro’s Apex One, OfficeScan, and Worry‑Free Business Security for Windows contain an improper access‑control flaw. An attacker who can write to a specific product folder can temporarily disable the security agent, invoke a Windows function, and gain elevated privileges on the host.
Exploitability – The vulnerability is publicly disclosed (CVE‑2020‑24557) and assigned a CVSS 3.1 base score of 7.8 (High). No public exploit code has been released, but the attack vector is straightforward for an adversary with local write access.
Affected Products – Trend Micro Apex One (Windows), Trend Micro OfficeScan (Windows), Trend Micro Worry‑Free Business Security (Windows).
Why It Matters for Trust & Control Assurance
- Access‑control hygiene – The flaw shows how a missing “only authorized users may modify security‑critical files” control can be leveraged to bypass protection, a control objective that appears in SOC 2, ISO 27001, NIST CSF, and many others.
- Audit‑ready evidence – Demonstrating that file‑system permissions are continuously monitored and that changes are logged provides defensible evidence during audits or third‑party assessments.
- Continuous assurance – Enterprises that can prove real‑time enforcement of least‑privilege policies reduce the risk of privilege‑escalation attacks and satisfy multiple framework requirements with a single control implementation.
Recommended Actions
- Patch immediately – Apply Trend Micro’s security update released for CVE‑2020‑24557.
- Validate file‑system permissions – Verify that only the service account can write to the product’s installation folder; remediate any over‑permissive ACLs.
- Enable and review privileged‑access logs – Ensure Windows Event Logging captures file‑system changes and privilege‑escalation attempts; retain logs for at least 90 days.
- Map to control objectives – Record the remediation steps against the “Access Control – Authorized Modification of Security‑Critical Assets” control in your internal control library.
Source: CISA KEV – CVE‑2020‑24557