Mozilla on March 20 released new security and stability updates for both versions of its Firefox browser and for its Internet application suite, SeaMonkey. The new updates eradicate a minor FTP PASV port-scanning vulnerability, a Mozilla spokesperson said.
A malicious Web page hosted on a specially coded FTP server could exploit this weakness to perform a rudimentary port-scan of machines inside the firewall of the victim.
By itself this causes no harm, but information about an internal network may be useful to an attacker should there be other vulnerabilities present on the network, the spokesperson said.
The FTP protocol includes the PASV (passive) command, which is used by Firefox to request an alternate data port. The specification of the FTP protocol allows the server response to include an alternate server address as well, although this is rarely used in practice.
With the update, Mozilla clients will now ignore the alternate server address, the spokesperson said.