Dalnet IRC Server "SUMMON" Buffer Overflow Vulnerability

Dalnet ircd is a server for a popular internet chat application, IRC (Internet Relay Chat). The implementation for one of its features, the "summon" command, has a hole which could grant an attacker remote access on the host running the server (with the privs of the server). The vulnerability is a buffer overflow (due to use of an sprintf with user input) and rather difficult to exploit. The reason for this is that the shellcode must be divided into a number of variables, one of them being the hostname (which is obtained via reverse lookup, so dns poisoning would be involved) and then reconstructed in memory and executed on the stack. Also, the "summons" command is not enabled in the ircd server by default -- it has to be defined at compile time. Nonetheless, in theory this can be exploited so patches should be applied.


 

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