stunnel < 5.14 Authentication Bypass Vulnerability
Medium Nessus Plugin ID 83730
SynopsisThe remote Windows host contains a program that is affected by an authentication bypass vulnerability.
DescriptionThe version of stunnel installed on the remote host is prior to version 5.14. It is, therefore, affected by a vulnerability related to the handling of authentication failures that involve the 'redirect' option. In this case, only the initial connection is forwarded to the hosts specified with 'redirect'; however, subsequent connections established with reused SSL/TLS sessions are forwarded to the hosts specified with 'connect' as if they were already successfully authenticated. A remote attacker can exploit this vulnerability to bypass authentication mechanisms.
Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.
SolutionUpgrade to stunnel 5.14 or later. Alternatively, remove the 'redirect' option from the configuration file.