Software Engineering Institute

The Microsoft Windows FTP Client does not properly validate the names of received files. If a remote attacker can persuade a user to download a file with a specially crafted name using the Windows FTP Client, that attacker may be able to write that file to an arbitrary location on the users system. In order to exploit this vulnerability, the crafted file name must map to an existing location on the user's system.

Note that this vulnerability may allow a remote attacker to execute arbitrary code. For instance, an attacker may be able to leverage this vulnerability to download an arbitrary file to the Startup folder. If the downloaded file is executable, then that file will be executed the next time a user logs in.

For more information, including a list of affected software, please see MS05-044. Please note that exploit code for this vulnerability is publicly available.

A remote attacker may be able to write files to arbitrary locations on a vulnerable system. If the target location is the Startup folder, then it is possible to cause arbitrary code to be automatically executed the next time the user logs in.

Apply a patch

Microsoft has addressed this issue in Microsoft Security Bulletin MS05-044

Do not download files from untrusted sources

By only downloading files from trusted sources, the chances of exploitation are reduced.