Martin von Gagern found a flow in how GnuTLS versions 1.2.4 up until 2.6.1 verified certificate chains provided by a server. A malicious server could use this flaw to spoof its identity by tricking client applications that used the GnuTLS library to trust invalid certificates . Update: It was found that the previously-published patch to correct this issue caused a regression when dealing with self-signed certificates. An updated patch that fixes the security issue and resolves the regression issue has been applied to these packages.