Hi All,

Does anyone has any update on this?


From: P, Sreelakshmi
Sent: Friday, December 7, 2018 4:19 PM
To: 'dnsmasq-discuss@lists.thekelleys.org.uk' 
Subject: Validation for malformed DHCP packets in dnsmasq


We are using dnsmasq 2.78. We see that there are some security vulnerability 
w.r.t malformed DHCP packets as explained below.

Problem 1:
A malformed dhcp discover packet can cause dhcp to be unresponsive from the 
switch for a small amount of time.  If this was repeated over time an attacker 
could make the dhcp service unresponsive DOSing the box.

It starts out with the malformed discover immediately followed by a dhcp 
decline.  then the client sends another dhcp discover packet.  The switch does 
not respond to this discover.
After about two seconds the client tries again and dhcp works as normal.

Problem 2:
DHCP request with anomaly causing DOS condition

A Malformed DHCP request causes dhcp server to not respond for a short period 
of time.  The request is modified by reducing the size of the data in the mac 
address field in the dhcp request.
After the request is sent to the switch the client sends another dhcp discover 
which is not responded to.  After about 1.5 seconds the client tries again and 
the discover is responded to.

Problem 3:
DHCP discover packet with extra byte in hardware address causing DOS of DHCP on 

If an extra byte is added to the hardware address field in a dhcp discover it 
will cause the DHCP service to become unresponsive for a short period of time.  
If repeated it could be used as a DOS attack.

Problem 4:
DHCPv6 solicit with anomaly in Identity association length field causing DOS

When the integer value 65534 is placed in the Identity association length field 
of a dhcpv6 solicit packet the switch enters a DOS state for a couple seconds

Problem 5:
DHCPv6 solicit 2 Extra bytes trailing option status code causes DOS

Sending dhcpv6 solicits with extra bytes trailing the option status code causes 
the switch dhcp server to become temporarily unresponsive.

In a summary, to overcome this problem, DHCP packet validation has to be done. 
Has any fix related to any of these problems have gone in after 2.78?

Thanks in Advance!!

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