Linux 2.4.x allows remote attackers to spoof the bridge Forwarding table via forged packets whose source addresses are the same as the target.
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A385
http://www.redhat.com/support/errata/RHSA-2003-239.html
http://www.redhat.com/support/errata/RHSA-2003-238.html
http://www.redhat.com/support/errata/RHSA-2003-198.html