External risk intelligence

ConfigServer Security & Firewall Remote Command Execution via Insecure Apache Configuration

CVE advisorySeverity: CRITICAL (CVSS 9.2)

CVE-2026-67402

The vulnerability exists in a firewall and security management tool's HTTPS virtual host. This service is designed to be public-facing to manage network security, making its web-based management interface an inherently internet-exposed service.

Halo Surface Signal: 5 out of 5 — more likely to be public-facing.

External exposure likelihood

Horizon Alert

Summary of the vulnerability and why it matters

This advisory concerns an insecure configuration within a firewall and security management tool that could allow an unauthorized remote attacker to execute arbitrary commands. The vulnerability arises from how the tool maps certain directories as executable programs, potentially enabling an attacker to run malicious code if their IP address is blocked. The main concern is confirming if your environment utilizes this specific configuration.

Insecure server mapping allows command execution.
Could impact system security if misconfigured.
Confirm relevance and exposure in your environment.

Attack Path

How an attacker could exploit the issue

An attacker whose IP address is blocked by ConfigServer Security & Firewall could potentially exploit this vulnerability. This is because an insecure configuration maps a system directory as executable CGI programs under a specific virtual host, allowing a remote unauthenticated attacker to request a mapped executable. If successful, this could enable the attacker to run arbitrary commands on the affected server with the privileges of the Apache user.

Attacker's IP must be blocked.
Request a mapped executable via HTTPS.
Arbitrary command execution.

Live Threat

Current exploitation, exposure, and threat context

When ConfigServer Security & Firewall's Messenger v3 HTTPS mode is enabled, a remote attacker whose address is blocked could exploit an insecure configuration to execute arbitrary commands as the Apache user. This could affect system integrity and potentially expose service behavior.

System data or services at risk.
Exploited via a mapped executable.
Arbitrary command execution.

Operational Fix

Recommended remediation, mitigation, and detection steps

This critical vulnerability in ConfigServer Security & Firewall's Messenger v3 HTTPS mode requires immediate attention. Infrastructure or platform teams managing CSF installations should first identify all instances running in HTTPS mode. Confirming network reachability and business criticality of these instances will help prioritize remediation efforts by pinpointing the accountable owner for each affected system.

Infrastructure/platform teams own remediation.
Verify CSF Messenger v3 HTTPS mode instances.
Plan remediation based on identified risk.

Supplementary metadata

CVSS vector

Validate whether this threat affects your internet-facing exposure.

Halo Threat Intelligence helps prioritize remediation with Halo Surface Signal and H/A/L/O context. Start exposure validation with a free external attack surface trial.

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Frequently asked questions

What is ConfigServer Security & Firewall?

ConfigServer Security & Firewall (CSF) is a security application used to manage server firewalls and block unauthorized access. It includes a feature called Messenger v3, which provides a web-based interface for interacting with users whose traffic is blocked. This tool is often integrated into hosting environments to simplify security management and automated blocking tasks.

How does CVE-2026-67402 work?

This vulnerability is classified as CWE-552, or Files or Directories Accessible to External Parties. It occurs because the software's Apache configuration incorrectly maps system directories containing executable programs as CGI scripts. This allows an unauthorized user to treat these system files as web requests, potentially tricking the server into running them and granting the attacker the ability to execute arbitrary commands.

Do I need to be blocked by the firewall to be at risk?

Yes, the vulnerability specifically impacts scenarios where an attacker's IP address is already blocked by the firewall. The flaw is not triggered by standard, unblocked traffic. If Messenger v3 is disabled, or if the HTTPS mode for the service is not in use, the specific insecure mapping that leads to this command execution path does not function, preventing the attack.

Is my server exposed to this threat?

Halo Surface Signal indicates that because this vulnerability exists within a firewall's HTTPS virtual host—a service inherently designed to be reachable via the internet to manage network security—it is considered highly likely to be internet-facing. You should evaluate any server where CSF Messenger v3 is active, as these public-facing management interfaces are the primary point of concern for this CVE.

How do I fix this security issue?

The primary response is to update your software to version 16.31 or later, as provided by WebPros. Before applying the update, infrastructure teams should audit their environments to identify all instances where CSF Messenger v3 is configured to use HTTPS mode. Prioritize updating these specific instances first, as they represent the active vulnerable surface described in this advisory.

References

support.cpanel.net/hc/en-us/articles/43171958716439-Security-CSF-Securit…

Written by Nicholas Merritt

Nicholas Merritt is VP of Security Solutions at Halo Security. With more than 25 years across application security, vulnerability prioritization, and offensive security, he helps teams translate threat data into practical exposure validation and remediation focus. He authors Halo Threat Intelligence CVE advisories using Halo Surface Signal and H/A/L/O context to prioritize internet-facing risk.