vsftpd vsf_filename_passes_filter Function Denial of Service
Medium Nessus Plugin ID 52704
SynopsisThe remote FTP server is prone to a denial of service attack.
DescriptionAccording to its self-reported version number, the instance of vsftpd listening on the remote server is earlier than 2.3.3 and, as such, may be affected by a denial of service vulnerability.
An error exists in the function 'vsf_filename_passes_filter()' in 'ls.c' that allows resource intensive glob expressions to be processed with the 'STAT' command. Using numerous IP addresses to bypass an FTP-sessions-per-IP-address limit, a remote attacker can carry out a denial of service attack.
Note that Nessus did not actually test for the flaw but instead has relied on the version in vsftpd's banner.
SolutionUpdate to vsftpd 2.3.4 or later. [While version 2.3.3 actually addresses this issue, 2.3.4 was released the same day to address a problem compiling the earlier version.]