Multiple buffer overflows in (a) UltraVNC (aka Ultr@VNC) 1.0.1 and earlier and (b) tabbed_viewer 1.29 (1) allow user-assisted remote attackers to execute arbitrary code via a malicious server that sends a long string to a client that connects on TCP port 5900, which triggers an overflow in Log::ReallyPrint; and (2) allow remote attackers to cause a denial of service (server crash) via a long HTTP GET request to TCP port 5800, which triggers an overflow in VNCLog::ReallyPrint.
https://www.exploit-db.com/exploits/1643
https://www.exploit-db.com/exploits/1642
https://exchange.xforce.ibmcloud.com/vulnerabilities/25650
https://exchange.xforce.ibmcloud.com/vulnerabilities/25648
http://www.vupen.com/english/advisories/2006/1240
http://www.securityfocus.com/archive/1/430711/100/0/threaded
http://www.securityfocus.com/archive/1/430287/100/0/threaded
http://www.securityfocus.com/archive/1/429930/100/0/threaded
http://securityreason.com/securityalert/674
http://secunia.com/advisories/19513
http://lists.grok.org.uk/pipermail/full-disclosure/2006-April/044901.html