Secunia advises that Sun has issued updated packages for Zebra. "An unspecified vulnerability exists in the Zebra telnet management service, which can be exploited to crash the service if a Zebra password has been enabled."
Updated packages can be found at ftp://ftp.cobalt.sun.com/pub/products/sunlinux/5.0/en/updates/i386/RPMS/zebra-0.91a-8.7.2.i386.rpm
and
ftp://ftp.cobalt.sun.com/pub/products/sunlinux/5.0/en/updates/i386/SRPMS/zebra-0.91a-8.7.2.src.rpm