Red Hat Bugzilla – Bug 443761
CVE-2008-1897 asterisk: 3-way handshake in IAX2 incomplete (CVE-2008-1923)
Last modified: 2008-06-19 08:57:50 EDT
Asterisk upstream published following security advisory AST-2008-006:
Javantea originally reported an issue in IAX2, whereby an attacker could send a
spoofed IAX2 NEW message, and Asterisk would start sending early audio to the
target address, without ever receiving an initial response. That original
vulnerability was addressed in June 2007, by requiring a response to the initial
NEW message before starting to send any audio.
Javantea subsequently found that we were doing insufficent verification of the
ACK response and that the ACK response could be spoofed, just like the initial
NEW message. We have addressed this failure with two changes. First, we have
started to require that the ACK response contains the unique source call number
that we send in our reply to the NEW message. Any ACK response that does not
contain the source call number that we have created will be silently thrown
away. Second, we have made the generation of our source call number a little
more difficult to predict, by randomly selecting a source call number, instead
of allocating them sequentially.
Fixed in: 22.214.171.124
asterisk-126.96.36.199-1.fc8 has been submitted as an update for Fedora 8
asterisk-188.8.131.52-1.fc7 has been submitted as an update for Fedora 7
CVE ids assigned by Mitre:
The IAX2 channel driver (chan_iax2) in Asterisk 1.2 before revision
72630 and 1.4 before revision 65679, when configured to allow
unauthenticated calls, sends "early audio" to an unverified source IP
address of a NEW message, which allows remote attackers to cause a
denial of service (traffic amplification) via a spoofed NEW message.
The IAX2 channel driver (chan_iax2) in Asterisk Open Source 1.0.x,
1.2.x before 1.2.28, and 1.4.x before 184.108.40.206; Business Edition
A.x.x, B.x.x before B.2.5.2, and C.x.x before C.1.8.1; AsteriskNOW
before 1.0.3; Appliance Developer Kit 0.x.x; and s800i before 220.127.116.11,
when configured to allow unauthenticated calls, does not verify that
an ACK response contains a call number matching the server's reply to
a NEW message, which allows remote attackers to cause a denial of
service (traffic amplification) via a spoofed ACK response that does
not complete a 3-way handshake. NOTE: this issue exists because of an
incomplete fix for CVE-2008-1923.
asterisk-18.104.22.168-1.fc7 has been pushed to the Fedora 7 stable repository. If problems still persist, please make note of it in this bug report.
asterisk-22.214.171.124-1.fc8 has been pushed to the Fedora 8 stable repository. If problems still persist, please make note of it in this bug report.
This issue was addressed in: