Cisco Security Advisory – The H.323 implementation in Cisco IOS Software contains a vulnerability that can be exploited remotely to cause a device that is running Cisco IOS Software to reload. Cisco has released free software updates that address this vulnerability. There are no workarounds to mitigate the vulnerability apart from disabling H.323 if the device that is running Cisco IOS Software does not need to run H.323 for VoIP services.
You can download this advisory from the following link: https://packetstormsecurity.com/files/download/81595/cisco-sa-20090923-h323.txt
Source: https://packetstormsecurity.com/files/81595/Cisco-Security-Advisory-20090923-h323.html