A method to bypass SSL certificate name vs. host name verification via NUL ('\0') character embedded in X509 certificate's CommonName or subjectAltName was presented at Black Hat USA 2009:

http://www.blackhat.com/html/bh-usa-09/bh-usa-09-archives.html#Marlinspike

Similar issues affects kdelibs' kssl. Problem only exists in handling of subjectAltNames, CommonNames with embedded NUL chars are handled correctly.

According to Thiago Macieira (maintainer of KDE's and Qt's SSL code), kssl is no longer used in current KDE4 versions, Qt's SSL code is used instead (which is affected by similar problem, see bug #520435).

Problem affects kdelibs 3.5.4 shipped in Red Hat Enterprise Linux 5. Versions in Red Hat Enterprise Linux 4 (3.3.1) and Red Hat Enterprise Linux 3 (3.1.3) are not affected, as they do not support subjectAltNames at all.

Unlike Qt, kssl is not prone to creation of universal MITM certificate (\0.whatever.com), as matching of '' wild card is limited to single host name component.