The vulnerable system is bound to the network stack and the set of possible attackers extends beyond the other options listed below, up to and including the entire Internet. Such a vulnerability is often termed “remotely exploitable” and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers). An example of a network attack is an attacker causing a denial of service by sending a specially crafted TCP packet across a wide area network (e.g., CVE-2004-0230).
Attack Complexity
Low
AC
The attacker must take no measurable action to exploit the vulnerability. The attack requires no target-specific circumvention to exploit the vulnerability. An attacker can expect repeatable success against the vulnerable system.
Privileges Required
None
PR
The attacker is unauthenticated prior to attack, and therefore does not require any access to settings or files of the vulnerable system to carry out an attack.
User Interaction
None
UI
The vulnerable system can be exploited without interaction from any human user, other than the attacker. Examples include: a remote attacker is able to send packets to a target system a locally authenticated attacker executes code to elevate privileges
Scope
Unchanged
S
An exploited vulnerability can only affect resources managed by the same security authority. In the case of a vulnerability in a virtualized environment, an exploited vulnerability in one guest instance would not affect neighboring guest instances.
Confidentiality
None
C
There is no impact on the confidentiality of the system; the attacker does not gain the ability to read any data.
Integrity
None
I
There is no impact on the integrity of the system; the attacker does not gain the ability to modify any files or information on the target system.
Availability
High
A
There is a total shutdown of the affected resource. The attacker can deny access to the system or data, potentially causing significant loss to the organization.
Asterisk Project Security Advisory - AST-2012-015
Product Asterisk
Summary Denial of Service Through Exploitation of Device
State Caching
Nature of Advisory Denial of Service
Susceptibility Remote Unauthenticated Sessions
Severity Critical
Exploits Known None
Reported On 26 July, 2012
Reported By Russell Bryant
Posted On 2 January, 2013
Last Updated On January 2, 2013
Advisory Contact Matt Jordan <mjordan AT digium DOT com>
CVE Name CVE-2012-5977
Description Asterisk maintains an internal cache for devices. The
device state cache holds the state of each device known to
Asterisk, such that consumers of device state information
can query for the last known state for a particular device,
even if it is not part of an active call. The concept of a
device in Asterisk can include things that do not have a
physical representation. One way that this currently occurs
is when anonymous calls are allowed in Asterisk. A device
is automatically created and stored in the cache for each
anonymous call that occurs; this is possible in the SIP and
IAX2 channel drivers and through channel drivers that
utilize the res_jabber/res_xmpp resource modules (Gtalk,
Jingle, and Motif). Attackers exploiting this vulnerability
can attack an Asterisk system configured to allow anonymous
calls by varying the source of the anonymous call,
continually adding devices to the device state cache and
consuming a system's resources.
Resolution Channels that are not associated with a physical device are
no longer stored in the device state cache. This affects
Local, DAHDI, SIP and IAX2 channels, and any channel drivers
built on the res_jabber/res_xmpp resource modules (Gtalk,
Jingle, and Motif).
Affected Versions
Product Release Series
Asterisk Open Source 1.8.x All Versions
Asterisk Open Source 10.x All Versions
Asterisk Open Source 11.x All Versions
Certified Asterisk 1.8.11 All Versions
Asterisk Digiumphones 10.x-digiumphones All Versions
Corrected In
Product Release
Asterisk Open Source 1.8.19.1, 10.11.1, 11.1.1
Certified Asterisk 1.8.11-cert10
Asterisk Digiumphones 10.11.1-digiumphones
Patches
SVN URL Revision
http://downloads.asterisk.org/pub/security/AST-2012-015-1.8.diff Asterisk
1.8
http://downloads.asterisk.org/pub/security/AST-2012-015-10.diff Asterisk
10
http://downloads.asterisk.org/pub/security/AST-2012-015-11.diff Asterisk
11
Links https://issues.asterisk.org/jira/browse/ASTERISK-20175
Asterisk Project Security Advisories are posted at
http://www.asterisk.org/security
This document may be superseded by later versions; if so, the latest
version will be posted at
http://downloads.digium.com/pub/security/AST-2012-015.pdf and
http://downloads.digium.com/pub/security/AST-2012-015.html
Revision History
Date Editor Revisions Made
19 November 2012 Matt Jordan Initial Draft
Asterisk Project Security Advisory - AST-2012-015
Copyright (c) 2012 Digium, Inc. All Rights Reserved.
Permission is hereby granted to distribute and publish this advisory in its
original, unaltered form.
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