OpenVPN versions before 2.3.15 and before 2.4.2 are vulnerable to reachable assertion when packet-ID counter rolls over resulting into Denial of Service of server by authenticated attacker.

Multiple cross-site request forgery (CSRF) vulnerabilities in the XML-RPC API in the Desktop Client in OpenVPN Access Server 1.5.6 and earlier allow remote attackers to hijack the authentication of administrators for requests that (1) disconnecting established VPN sessions, (2) connect to arbitrary VPN servers, or (3) create VPN profiles and execute arbitrary commands via crafted API requests.

OpenVPN 2.x before 2.0.11, 2.1.x, 2.2.x before 2.2.3, and 2.3.x before 2.3.6 allows remote authenticated users to cause a denial of service (server crash) via a small control channel packet.

Cross-site request forgery (CSRF) vulnerability in the Admin web interface in OpenVPN Access Server before 1.8.5 allows remote attackers to hijack the authentication of administrators for requests that create administrative users.

The openvpn_decrypt function in crypto.c in OpenVPN 2.3.0 and earlier, when running in UDP mode, allows remote attackers to obtain sensitive information via a timing attack involving an HMAC comparison function that does not run in constant time and a padding oracle attack on the CBC mode cipher.

The interactive service in OpenVPN 2.6.9 and earlier allows an attacker to send data causing a stack overflow which can be used to execute arbitrary code with more privileges.

The interactive service in OpenVPN 2.6.9 and earlier allows the OpenVPN service pipe to be accessed remotely, which allows a remote attacker to interact with the privileged OpenVPN interactive service.

OpenVPN Access Server before 2.11 uses a weak random generator used to create user session token for the web portal

The OpenVPN Access Server installer creates a log file readable for everyone, which from version 2.10.0 and before 2.11.0 may contain a random generated admin password

OpenVPN Access Server 2.10 and prior versions are susceptible to resending multiple packets in a response to a reset packet sent from the client which the client again does not respond to, resulting in a limited amplification attack.

OpenVPN Access Server 2.9.0 through 2.9.4 allow remote attackers to inject arbitrary web script or HTML via the web login page URL.

OpenVPN before version 2.5.3 on Windows allows local users to load arbitrary dynamic loadable libraries via an OpenSSL configuration file if present, which allows the user to run arbitrary code with the same privilege level as the main OpenVPN process (openvpn.exe).

OpenVPN 3 Core Library version 3.6 and 3.6.1 allows a man-in-the-middle attacker to bypass the certificate authentication by issuing an unrelated server certificate using the same hostname found in the verify-x509-name option in a client configuration.

OpenVPN Access Server 2.8.x before 2.8.1 allows LDAP authentication bypass (except when a user is enrolled in two-factor authentication).

OpenVPN Access Server 2.7.3 to 2.8.7 allows remote attackers to trigger an assert during the user authentication phase via incorrect authentication token data in an early phase of the user authentication resulting in a denial of service.

Control Channel in OpenVPN 2.4.7 and earlier allows remote attackers to cause a denial of service via crafted reset packet.

OpenVPN 2.5.1 and earlier versions allows a remote attackers to bypass authentication and access control channel data on servers configured with deferred authentication, which can be used to potentially trigger further information leaks.

OpenVPN Access Server 2.8.7 and earlier versions allows a remote attackers to bypass authentication and access control channel data on servers configured with deferred authentication, which can be used to potentially trigger further information leaks.

OpenVPN Access Server older than version 2.8.4 and version 2.9.5 generates new user authentication tokens instead of reusing exiting tokens on reconnect making it possible to circumvent the initial token expiry timestamp.

An issue was discovered in OpenVPN 2.4.x before 2.4.9. An attacker can inject a data channel v2 (P_DATA_V2) packet using a victim's peer-id. Normally such packets are dropped, but if this packet arrives before the data channel crypto parameters have been initialized, the victim's connection will be dropped. This requires careful timing due to the small time window (usually within a few seconds) between the victim client connection starting and the server PUSH_REPLY response back to the client. This attack will only work if Negotiable Cipher Parameters (NCP) is in use.