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
The product uses a function that accepts a format string as an argument, but the format string originates from an external source.
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Openvpn | Openvpn | * | 2.4.5 (including) |
| Openvpn | Ubuntu | artful | * |
| Openvpn | Ubuntu | bionic | * |
| Openvpn | Ubuntu | devel | * |
| Openvpn | Ubuntu | esm-infra-legacy/trusty | * |
| Openvpn | Ubuntu | esm-infra/bionic | * |
| Openvpn | Ubuntu | esm-infra/xenial | * |
| Openvpn | Ubuntu | precise/esm | * |
| Openvpn | Ubuntu | trusty | * |
| Openvpn | Ubuntu | trusty/esm | * |
| Openvpn | Ubuntu | xenial | * |
When an attacker can modify an externally-controlled format string, this can lead to buffer overflows, denial of service, or data representation problems. It should be noted that in some circumstances, such as internationalization, the set of format strings is externally controlled by design. If the source of these format strings is trusted (e.g. only contained in library files that are only modifiable by the system administrator), then the external control might not itself pose a vulnerability.