CVE-2018-7544: Critical severity OpenVPN OpenVPN vulnerability
DISPUTED A cross-protocol scripting issue was discovered in the management interface in OpenVPN through 2.4.5. When this interface is enabled over TCP without a password, and when no other clients are connected to this interface, attackers can execute arbitrary management commands, obtain sensitive information, or cause a denial of service (SIGTERM) by triggering XMLHttpRequest actions in a web browser. This is demonstrated by a multipart/form-data POST to http://localhost:23000 with a "signal SIGTERM" command in a TEXTAREA element. NOTE: The vendor disputes that this is a vulnerability. They state that this is the result of improper configuration of the OpenVPN instance rather than an intrinsic vulnerability, and now more explicitly warn against such configurations in both the management-interface documentation, and with a runtime warning.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Configuration
Do not enable the OpenVPN management interface over TCP without a password; configure authentication (password) so unauthenticated clients cannot execute management commands.
OpenVPN management interface transport over TCP (management interface) = enable only with password - Configuration
Ensure the management interface is accessible only to trusted clients; the described impact assumes the interface is enabled over TCP without a password and no other clients are connected.
OpenVPN management interface management interface access control (clients connected) = ensure trusted access only - Compensating control
Restrict network access to the OpenVPN management interface (e.g., firewall/ACL to allow only trusted hosts) so attackers cannot reach http://localhost:23000 from untrusted parties.
Event History
Frequently Asked Questions
What is the vulnerability ID for this issue?
The vulnerability ID for this issue is CVE-2018-7544.
What is the severity of CVE-2018-7544?
The severity of CVE-2018-7544 is critical, with a severity value of 9.1.
What is the affected software for CVE-2018-7544?
The affected software for CVE-2018-7544 is OpenVPN version 2.4.5.
What is the description of CVE-2018-7544?
CVE-2018-7544 is a cross-protocol scripting issue in the management interface of OpenVPN through version 2.4.5, allowing attackers to execute arbitrary management commands.
How can I fix CVE-2018-7544?
To fix CVE-2018-7544, it is recommended to update OpenVPN to a version that is not affected by this vulnerability.