David Leadbeater discovered an integer underflow that could be triggered via the LINKS command and can lead to a denial of service or the execution of arbitrary code . This issue affects both, ircd-hybrid and ircd-ratbox. It was discovered that the ratbox IRC server is prone to a denial of service attack via the HELP command. The ircd-hybrid package is not vulnerable to this issue . For the stable distribution , this problem has been fixed in version 1:7.2.2.dfsg.2-4+lenny1 of the ircd-hybrid package and in version 2.2.8.dfsg-2+lenny1 of ircd-ratbox. Due to a bug in the archive software it was not possible to release the fix for the oldstable distribution simultaneously. The packages will be released as version 7.2.2.dfsg.2-3+etch1 once they become available. For the testing distribution and the unstable distribution , this problem will be fixed soon. We recommend that you upgrade your ircd-hybrid/ircd-ratbox packages.