A new version of Wireshark (Ethereal) has been released to address multiple security issues.

"Impact

It may be possible to make Wireshark crash by injecting a series of malformed packets onto the wire or by convincing someone to read a malformed packet trace file.

 Resolution

Upgrade to Wireshark 1.0.4 or later. Due to the nature of the bugs, there is no workaround for previous versions."

More Info: http://www.wireshark.org/news/20081020.html
Advisory: http://www.wireshark.org/security/wnpa-sec-2008-06.html
Download: http://www.wireshark.org/download.html