Fedora 23: FEDORA-2015-7a89e8db70 Critical: Proftpd Memory Issue

ProFTPD is an enhanced FTP server with a focus toward simplicity, security,

and ease of configuration. It features a very Apache-like configuration

syntax, and a highly customizable server infrastructure, including support for

multiple 'virtual' FTP servers, anonymous FTP, and permission-based directory

visibility.

This package defaults to the standalone behavior of ProFTPD, but all the

needed scripts to have it run by systemd instead are included.

Part of the SFTP handshake involves "extensions", which are key/value pairs, comprised of strings. In SSH, strings are encoded for network transport as a 32-bit length, followed by the bytes. The mod_sftp module currently places no bounds/length limitations when reading these SFTP extension key/value data from the network. A malicious attacker might attempt to encode large values, and allocate more memory than is necessary, causing excessive resource usage or the FTP daemon to crash. This update limits the amount of memory allocated to handle these extensions.