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 1.4.19.1; 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 1.1.0.3, 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.

The remote host is affected by the vulnerability described in GLSA-200905-01 (Asterisk: Multiple vulnerabilities)

    Multiple vulnerabilities have been discovered in the IAX2 channel     driver when performing the 3-way handshake (CVE-2008-1897), when     handling a large number of POKE requests (CVE-2008-3263), when handling     authentication attempts (CVE-2008-5558) and when handling firmware     download (FWDOWNL) requests (CVE-2008-3264). Asterisk does also not     correctly handle SIP INVITE messages that lack a 'From' header     (CVE-2008-2119), and responds differently to a failed login attempt     depending on whether the user account exists (CVE-2008-3903,     CVE-2009-0041).
  Impact :

    Remote unauthenticated attackers could send specially crafted data to     Asterisk, possibly resulting in a Denial of Service via a daemon crash,     call-number exhaustion, CPU or traffic consumption. Remote     unauthenticated attackers could furthermore enumerate valid usernames     to facilitate brute-force login attempts.
  Workaround :

    There is no known workaround at this time.

This security update fixes multiple security vulnerabilities in asterisk (CVE-2008-1897, CVE-2008-2119, CVE-2008-3263, CVE-2008-3264).

The version of Asterisk running on the remote host does not properly validate an IAX2 handshake.  By spoofing NEW and ACK messages, an unauthenticated, remote attacker may be able to leverage this issue to flood a third-party host with packets from the affected host containing audio data.

Joel R. Voss discovered that the IAX2 module of Asterisk, a free software PBX and telephony toolkit performs insufficient validation of IAX2 protocol messages, which may lead to denial of service.

Fixes security bug found in IAX2:
http://downloads.digium.com/pub/security/AST-2008-006.html

Note that Tenable Network Security has extracted the preceding description block directly from the Fedora security advisory. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.

ID	Name	Product	Family	Severity
38677	GLSA-200905-01 : Asterisk: Multiple vulnerabilities	Nessus	Gentoo Local Security Checks	high
33894	openSUSE 10 Security Update : asterisk (asterisk-5524)	Nessus	SuSE Local Security Checks	high
32132	Asterisk IAX2 Multiple Method Handshake Spoofing DoS	Nessus	Denial of Service	medium
32125	Debian DSA-1563-1 : asterisk - programming error	Nessus	Debian Local Security Checks	medium
32102	Fedora 8 : asterisk-1.4.19.1-1.fc8 (2008-3390)	Nessus	Fedora Local Security Checks	medium
32098	Fedora 7 : asterisk-1.4.19.1-1.fc7 (2008-3365)	Nessus	Fedora Local Security Checks	medium

Detections

Analytics

CVE-2008-1897

high

Tenable Plugins

high

high

medium

medium

medium

medium