“The certificate used by NetNanny is shared among all installations of NetNanny,” said Garret Wassermann, a vulnerability analyst at CERT. He added that " the private key used to generate the certificate is also shared and may be obtained in plain text directly from the software.”
An attacker can easily exploit this limitation to generate new certificates just by accessing the software. The spoofed certificate signed by NetNanny would appear to be trustworthy and might lead the user to a malicious site which is faking as a secure HTTPS site. Moreover, the attacker could intercept HTTPS traffic o carry out man in the middle attacks in the affected system without browser certificate warnings being triggered by the system.
The software, launched in 1995 is widely used by parents to filter internet services for their children. Presently the version 188.8.131.52 has been found to be vulnerable, as warned by CERT but other builds might be affected as well.Questions regarding a fix on the issue remains unanswered by ContentWatch, the dedeveloping company.
The users are strongly advised to remove NetNanny or at least remove the bogus certificates created by the service or to disable SSL filtering and manually remove certificates from there.