ROS-2-816

2.816 OpenVPN Authentication Bypass (CVE-2020-15078)

1. Vulnerability Description:

The vulnerability allows a remote attacker to bypass authentication and access restrictions to leak VPN configuration data. The issue only occurs on servers that are configured to use deferred_auth. Under certain circumstances, an attacker can force the server to return a PUSH_REPLY message with VPN configuration data before sending the AUTH_FAILED message. Combined with the use of the “–auth-gen-token” parameter or a user’s own token-based authentication scheme, the vulnerability could lead to access to the VPN using a non-working account: BDU:2021-02221

2. Possible measures to eliminate the vulnerability

Prohibit the use of deferred authentication when using Openvpn or - install security updates for the package (with dependencies if necessary): openvpn**Installing updates is possible in the following ways:**a) if the computer with the installed OS version has access to the vendor’s official repository, you should run the update as administrator with the command:# yum updateAfter the list of updated packages is displayed, agree to apply updates by pressing the Y key on the keyboard. Wait until the update installation is complete and make sure that there are no errors during its installation.b)If the computer with the installed OS version does not have access to the vendor’s official repository, you should perform the following actions: - download the updated package (with dependencies if necessary): http://repo.red-soft.ru/redos/7.2c/x86_64/updates/openvpn-2.4.11-1.el7.x86_64.rpm Check the integrity and authenticity of the package according to instructionsInstall the downloaded package(s) with the command:# yum localinstall *.rpmWhen the list of updated packages is displayed, agree to apply the updates by pressingY on the keyboard. Wait for the updates to finish installing and make sure there are no errors during the installation.

Date of last modification: 08.09.2021