Re: Security flaw in ALCATEL/THOMSON Speed Touch Pro ADSL modems

[3APA3A <3APA3A () SECURITY NNOV RU>]

Dear Gregory Duchemin,

In case of the product like ADSL modem is, it's not a bug, but a leak of
feature  to  secure  DHCP and/or dynamic DNS updates, because it's a way
DHCP  and DNS are supposed to work and it's impossible to fix it without
implementing  protocol  extensions.  This products are targeted for SOHO
(any corporate user already have DNS/DHCP server implemented) where this
kind of attack does not lead to any serious threats.

--Friday, November 12, 2004, 9:02:28 AM, you wrote to bugtraq () securityfocus com:


GD> Upon complete DHCP negociation, Alcatel modem will try to register the
GD> client's DHCP HOSTNAME option into its local DNS domain.
GD> At this point, it will care about the hostname syntax and will also
GD> check it for redundancy.
GD> It will simply discard any DNS dynamic update if the proposed hostname
GD> already exists.
GD> If it doesn't, an entry is added to the end of the local zone file.
GD> However any new DHCP request for an already existing lease, including
GD> a redundant HOSTNAME, will bypass this checking.
GD> We have now two entries with the same hostname but two differents ip
GD> addresses.

-- 
~/ZARAZA
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