OpenVPN before 2.0.1, when running with "verb 0" and without TLS authentication, does not properly flush the OpenSSL error queue when a client fails certificate authentication to the server and causes the error to be processed by the wrong client, which allows remote attackers to cause a denial of service (client disconnection) via a large number of failed authentication attempts.
Severity
Medium 5.0
Published
24 Aug 2005
Last changed
16 Jun 2026
Added to UpHeron
1 Nov 2026
Exploit chance
2% in the next 30 daysHigher than 80% of CVEs. EPSS by FIRST, 12 Nov 2026
Attack
Over the network · No login needed
Attacker can
Slow it down
CVSS vector
AV:N/AC:L/Au:N/C:N/I:N/A:P
Sources
NVD
Affected software
Software
Affected versions
OpenVPNServers and applications · cpe:a:openvpn:openvpn