Ethereal is a feature rich network protocol analyzer.
There are multiple vulnerabilities in versions of Ethereal earlier than 0.10.4, including:
An attacker could use these vulnerabilities to crash Ethereal or even execute arbitrary code with the permissions of the user running Ethereal, which could be the root user.
For a temporary workaround you can disable all affected protocol dissectors by selecting Analyze->Enabled Protocols... and deselecting them from the list. However, it is strongly recommended to upgrade to the latest stable release.
All Ethereal users should upgrade to the latest stable version:
# emerge sync
# emerge -pv ">=net-analyzer/ethereal-0.10.4"
# emerge ">=net-analyzer/ethereal-0.10.4"