The ASN.1 parser in Ethereal 0.9.2 and earlier allows remote attackers to cause a denial of service (crash) via a certain malformed packet, which causes Ethereal to allocate memory incorrectly, possibly due to zero-length fields.
http://www.securityfocus.com/bid/4604
http://www.redhat.com/support/errata/RHSA-2002-088.html
http://www.iss.net/security_center/static/8952.php
http://www.ethereal.com/appnotes/enpa-sa-00003.html
http://www.debian.org/security/2002/dsa-130
http://distro.conectiva.com.br/atualizacoes/?id=a&anuncio=000474