Trend Micro Apex One and OfficeScan Arbitrary File Write and Authentication Bypass Vulnerability (CVE-2020-8599) Security Advisory
Executive & SecOps Summary
SECOPS ASSESSMENTTrend Micro Apex One (2019) and OfficeScan XG servers.
Unauthenticated remote attackers can write arbitrary data to arbitrary paths, bypassing ROOT login and achieving full system compromise.
Immediately apply the official Trend Micro Critical Patches (CP) and restrict access to management ports.
Affected Products & Version Scope
Remediation & Live Workaround Commands
PATCH & WORKAROUND1. Official Patch & Version Upgrade Commands
Download and install the latest Critical Patch (CP) or Service Pack from the official Trend Micro Support Portal. Use the following PowerShell commands to verify and manage the relevant services during the update process.
# Check the status of Apex One / OfficeScan core services
Get-Service -Name 'OfcService', 'TMBMServer' | Select-Object Name, DisplayName, Status
# Stop the main service safely before applying the patch
Stop-Service -Name 'OfcService' -Force2. Temporary Workaround & Hardening Configuration
If immediate patching is not feasible, restrict access to the Apex One/OfficeScan management console ports (default TCP 4343, 8080) using firewall rules to block untrusted external traffic.
# Block external access to Apex One management port (TCP 4343) and allow only trusted admin IP
New-NetFirewallRule -DisplayName 'Block_ApexOne_External' -Direction Inbound -LocalPort 4343 -Protocol TCP -Action Block
New-NetFirewallRule -DisplayName 'Allow_Admin_ApexOne' -Direction Inbound -LocalPort 4343 -Protocol TCP -RemoteAddress '192.168.10.50' -Action Allow3. Log Audit & IoC Verification Commands
Inspect the server directories for unauthorized file creations or modifications, and audit IIS logs for anomalous POST requests.
# Search for .exe, .dll, .asp, or .aspx files created or modified in the last 7 days
Get-ChildItem -Path 'C:\Program Files (x86)\Trend Micro\' -Recurse -Include *.exe, *.dll, *.asp, *.aspx | Where-Object { $_.LastWriteTime -gt (Get-Date).AddDays(-7) } | Select-Object FullName, LastWriteTimeBlock Kernel Privilege Escalation & Ransomware Payloads Before You Can Reboot
Protect unpatched Windows, Linux, and macOS workloads against in-memory exploitation and lateral movement with autonomous EDR.
Technical Root Cause & Exploitation Mechanics
1. Vulnerability Overview & Root Cause
This vulnerability (CVE-2020-8599) exists in a specific executable (.exe) file within Trend Micro Apex One (2019) and OfficeScan XG servers due to insufficient input validation. An unauthenticated remote attacker can exploit this flaw by sending crafted requests to write arbitrary data to arbitrary paths on the affected installation, leading to authentication bypass and ROOT login takeover.
2. Exploitation Mechanics & Attack Scenario
Exploitation of this vulnerability does not require authentication. An attacker transmits malicious payloads directly to the vulnerable binary over the network. By manipulating file path and content parameters, the attacker can write arbitrary files (such as web shells or malicious executables) into sensitive directories (e.g., web root or startup folders). This allows the attacker to execute arbitrary code or overwrite session tokens to bypass the login mechanism entirely and gain ROOT-level administrative access.
3. Infrastructure & Business Impact
With a CVSS score of 9.8 (Critical) and its inclusion in the CISA KEV catalog, this vulnerability poses an extreme risk. Successful exploitation grants full control over the endpoint security management server. Attackers can disable endpoint protection across the entire enterprise, establish a persistent foothold for lateral movement, deploy ransomware, or exfiltrate sensitive corporate data.
Official Vendor Advisories & References
Trend Micro Apex One (2019) and OfficeScan XG server contain a vulnerable EXE file that could allow a remote attacker to write arbitrary data to an arbitrary path on affected installations and bypass ROOT login. Authentication is not required to exploit this vulnerability.
Frequently Asked SecOps Questions (CVE-2020-8599)
FAQQ1. How critical is CVE-2020-8599 and is it actively exploited in the wild?
CVE-2020-8599 is rated CVSS 9.8 (CRITICAL) with a 30-day EPSS exploitation probability of 11.9%. It is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, requiring immediate emergency remediation.
Q2. Which vendors and products are affected by CVE-2020-8599?
Primary impacted vendors include trendmicro across apex_one, officescan. Scope summary: All unpatched installations of Trend Micro Apex One (2019) and OfficeScan XG servers
Q3. What temporary mitigations or workarounds exist for CVE-2020-8599 before patching?
[Mitigation] Immediately apply the official Trend Micro Critical Patches (CP) and restrict access to management ports. Follow the CLI remediation commands and interactive SecOps checklist on this page to restrict exposure prior to your maintenance window.
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