Stunnel, a program designed to work as an universal SSL tunnel for network daemons, is prone to a buffer overflow vulnerability when using the Microsoft NT LAN Manager (NTLM) authentication (protocolAuthentication = NTLM) together with the connect protocol method (protocol = connect). With these prerequisites and using stunnel4 in SSL client mode (client = yes ) on a 64 bit host, an attacker could possibly execute arbitrary code with the privileges of the stunnel process, if the attacker can either control the specified proxy server or perform man-in-the-middle attacks on the tcp session between stunnel and the proxy sever. Note that for the testing distribution (wheezy) and the unstable distribution (sid), stunnel4 is compiled with stack smashing protection enabled, which should help protect against arbitrary code execution.

For the stable distribution (squeeze), this problem has been fixed in version 3:4.29-1+squeeze1. For the testing distribution (wheezy), this problem has been fixed in version 3:4.53-1.1. For the unstable distribution (sid), this problem has been fixed in version 3:4.53-1.1. We recommend that you upgrade your stunnel4 packages.

The stunnel program is designed to work as SSL encryption wrapper between remote client and local (inetd-startable) or remote server. The concept is that having non-SSL aware daemons running on your system you can easily setup them to communicate with clients over secure SSL channel.

stunnel4 on Debian Linux

This check tests the installed software version using the apt package manager.

• http://www.debian.org/security/2013/dsa-2664.html

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Updated on 2015-03-25