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
High
PR
The attacker requires privileges that provide significant (e.g., administrative) control over the vulnerable system allowing full access to the vulnerable system’s settings and files.
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
High
C
There is total information disclosure, resulting in all data on the system being revealed to the attacker, or there is a possibility of the attacker gaining control over confidential data.
Integrity
High
I
There is a total compromise of system integrity. There is a complete loss of system protection, resulting in the attacker being able to modify any file 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-2012-014
Product Asterisk
Summary Crashes due to large stack allocations when using
TCP
Nature of Advisory Stack Overflow
Susceptibility Remote Unauthenticated Sessions (SIP)
Remote Authenticated Sessions (XMPP, HTTP)
Severity Critical
Exploits Known No
Reported On 7 November, 2012
Reported By Walter Doekes
Posted On 2 January, 2013
Last Updated On January 2, 2013
Advisory Contact Mark Michelson <mmichelson AT digium DOT com>
CVE Name CVE-2012-5976
Description Asterisk has several places where messages received over
various network transports may be copied in a single stack
allocation. In the case of TCP, since multiple packets in a
stream may be concatenated together, this can lead to large
allocations that overflow the stack.
In the case of SIP, it is possible to do this before a
session is established. Keep in mind that SIP over UDP is
not affected by this vulnerability.
With HTTP and XMPP, a session must first be established
before the vulnerability may be exploited. The XMPP
vulnerability exists both in the res_jabber.so module in
Asterisk 1.8, 10, and 11 as well as the res_xmpp.so module
in Asterisk 11.
Resolution Stack allocations when using TCP have either been eliminated
in favor of heap allocations or have had an upper bound
placed on them to ensure that the stack will not overflow.
For SIP, the allocation now has an upper limit.
For HTTP, the allocation is now a heap allocation instead of
a stack allocation.
For XMPP, the allocation has been eliminated since it was
unnecessary.
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 SIP: unaffected
HTTP and XMPP: 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-2012-014-1.8.diff Asterisk
1.8
http://downloads.asterisk.org/pub/security/AST-2012-014-10.diff Asterisk
10
http://downloads.asterisk.org/pub/security/AST-2012-014-11.diff Asterisk
11
Links https://issues.asterisk.org/jira/browse/ASTERISK-20658
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-2012-014.pdf and
http://downloads.digium.com/pub/security/AST-2012-014.html
Revision History
Date Editor Revisions Made
19 November, 2012 Mark Michelson Initial Draft
02 January, 2013 Matt Jordan Removed ABE from affected products
Asterisk Project Security Advisory - AST-2012-014
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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