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Date: Wed, 06 Apr 2011 20:18:12 +0200
From: Jan Lieskovsky <>
CC: "Steven M. Christey" <>,
        Jiri Popelka <>
Subject: Re: CVE Request -- dhcp: DoS (excessive CPU use) by
 opening an OMAPI connection

Jan Lieskovsky wrote:
> Hello Josh, Steve, vendors,
>   A security flaw was found in the way DHCP (Dynamic Host Configuration 
> Protocol)
> server processed remote connections when the dhcpd was configured to 
> provide
> Object Management API (OMAPI) capability. A remote attacker could use 
> this flaw
> to cause denial of service (excessive CPU use and dhcpd daemon 
> unreachability).
> References:
> [1]
> [2]
> [3]
> [4]
> [5]
> Note: Though looks as minor / low severity issue, under proper 
> configuration
>       looks to be a way, how to get dhcpd completely unresponsive for 
> further
>       requests.
> Could you allocate a CVE id for this? (though opened for discussion if this
> being more to be a bug, than a real security issue).

The dhcpd(8) manual page:

suggests it's possible to "The control object allows you to shut the server down."
[the Control Object section], but it also states:

"OMAPI clients connect to the server using TCP/IP, authenticate, and can then
examine the server's current status and make changes to it."


"The DHCP server exports the following objects: lease, host, failover-state and group."

so not sure, if any (unprivileged) OMAPI client could shut down the server.

Hopefully Jiri / someone else more familiar with OMAPI feature could shed more
light into this (if each OMAPI client is able to shut down the dhcpd server => just bug
or just privileged / authenticated one => potential DoS).

Thanks && Regards, Jan.
Jan iankko Lieskovsky / Red Hat Security Response Team

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