Avahi 0.7 missing link-local checks in Legacy Unicast Responses cause information disclosure and makes DDoS with mDNS traffic reflection possible

[Krzysztof Burghardt <krzysztof () burghardt pl>]

Hi!

Avahi-daemon in Avahi through 0.7 inadvertently sends Legacy Unicast
Responses to IPv4 unicast queries with source addresses that are not
link-local, which allows remote attackers to cause a denial of service
(traffic amplification) or obtain potentially sensitive information
via port-5353 UDP packets.

send(IP(src="1.1.1.1",dst="192.168.1.1")/UDP(sport=53,
dport=5353)/DNS(rd=1,qd=DNSQR(qtype="PTR", qname="_ssh._tcp.local.")))

Author was notified by his bug tracker:
https://github.com/lathiat/avahi/issues/203

Regards,
-- 
Krzysztof Burghardt <krzysztof () burghardt pl>
http://www.burghardt.pl/