FastNetMon Community Edition versions through 1.2.9 are vulnerable to a local symlink attack because the statistics file path defaults to a predictable location in /tmp ('/tmp/fastnetmon.dat'). The function print_screen_contents_into_file() truncates and writes to this file without checking for symbolic links or using safe file open flags like O_NOFOLLOW. Additionally, a bug causes chmod() to apply permissions incorrectly, and the daemon sets umask to 0, making created files world-writable. These factors combined allow a local attacker to exploit the vulnerability to overwrite arbitrary files as the FastNetMon process user, which is typically root.

A local attacker can leverage this vulnerability to overwrite arbitrary files on the system with the privileges of the FastNetMon process user, typically root. This can lead to privilege escalation or system compromise depending on which files are overwritten. There is no indication of known exploits in the wild at this time.

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until a fix is available, restrict local access to the system and consider monitoring or restricting the /tmp directory usage by FastNetMon. Avoid running FastNetMon with root privileges if possible. No official fix or temporary workaround has been provided in the available data.