Asterisk Project Security Advisory - On certain implementations of libc, the scanf family of functions uses an unbounded amount of stack memory to repeatedly allocate string buffers prior to conversion to the target type. Coupled with Asterisk's allocation of thread stack sizes that are smaller than the default, an attacker may exhaust stack memory in the SIP stack network thread by presenting excessively long numeric strings in various fields.
b1dc46b65ba0899d179d5df802c216ac411cd9b7c37c701cd854541313c4d1e2 Asterisk Project Security Advisory - AST-2009-005
+------------------------------------------------------------------------+
| Product | Asterisk |
|---------------------+--------------------------------------------------|
| Summary | Remote Crash Vulnerability in SIP channel driver |
|---------------------+--------------------------------------------------|
| Nature of Advisory | Denial of Service |
|---------------------+--------------------------------------------------|
| Susceptibility | Remote Unauthenticated Sessions |
|---------------------+--------------------------------------------------|
| Severity | Critical in 1.6.1; minor in lesser versions |
|---------------------+--------------------------------------------------|
| Exploits Known | No |
|---------------------+--------------------------------------------------|
| Reported On | July 28, 2009 |
|---------------------+--------------------------------------------------|
| Reported By | Nick Baggott < nbaggott AT mudynamics DOT com > |
|---------------------+--------------------------------------------------|
| Posted On | August 10, 2009 |
|---------------------+--------------------------------------------------|
| Last Updated On | August 10, 2009 |
|---------------------+--------------------------------------------------|
| Advisory Contact | Tilghman Lesher < tlesher AT digium DOT com > |
|---------------------+--------------------------------------------------|
| CVE Name | CVE-2009-2726 |
+------------------------------------------------------------------------+
+------------------------------------------------------------------------+
| Description | On certain implementations of libc, the scanf family of |
| | functions uses an unbounded amount of stack memory to |
| | repeatedly allocate string buffers prior to conversion |
| | to the target type. Coupled with Asterisk's allocation |
| | of thread stack sizes that are smaller than the default, |
| | an attacker may exhaust stack memory in the SIP stack |
| | network thread by presenting excessively long numeric |
| | strings in various fields. |
| | |
| | Note that while this potential vulnerability has existed |
| | in Asterisk for a very long time, it is only potentially |
| | exploitable in 1.6.1 and above, since those versions are |
| | the first that have allowed SIP packets to exceed 1500 |
| | bytes total, which does not permit strings that are |
| | large enough to crash Asterisk. (The number strings |
| | presented to us by the security researcher were |
| | approximately 32,000 bytes long.) |
| | |
| | Additionally note that while this can crash Asterisk, |
| | execution of arbitrary code is not possible with this |
| | vector. |
+------------------------------------------------------------------------+
+------------------------------------------------------------------------+
| Resolution | Upgrade Asterisk to one of the releases listed below. |
+------------------------------------------------------------------------+
+------------------------------------------------------------------------+
| Affected Versions |
|------------------------------------------------------------------------|
| Product | Release | |
| | Series | |
|----------------------------+------------+------------------------------|
| Asterisk Open Source | 1.2.x | All versions prior to 1.2.34 |
|----------------------------+------------+------------------------------|
| Asterisk Open Source | 1.4.x | All versions prior to |
| | | 1.4.26.1 |
|----------------------------+------------+------------------------------|
| Asterisk Open Source | 1.6.0.x | All versions prior to |
| | | 1.6.0.12 |
|----------------------------+------------+------------------------------|
| Asterisk Open Source | 1.6.1.x | All versions prior to |
| | | 1.6.1.4 |
|----------------------------+------------+------------------------------|
| Asterisk Addons | 1.2.x | Not affected |
|----------------------------+------------+------------------------------|
| Asterisk Addons | 1.4.x | Not affected |
|----------------------------+------------+------------------------------|
| Asterisk Addons | 1.6.0.x | Not affected |
|----------------------------+------------+------------------------------|
| Asterisk Addons | 1.6.1.x | Not affected |
|----------------------------+------------+------------------------------|
| Asterisk Business Edition | A.x.x | All versions |
|----------------------------+------------+------------------------------|
| Asterisk Business Edition | B.x.x | All versions prior to |
| | | B.2.5.9 |
|----------------------------+------------+------------------------------|
| Asterisk Business Edition | C.2.x | All versions prior to |
| | | C.2.4.1 |
|----------------------------+------------+------------------------------|
| Asterisk Business Edition | C.3.x | All versions prior to C.3.1 |
|----------------------------+------------+------------------------------|
| AsteriskNOW | 1.5 | Not affected |
|----------------------------+------------+------------------------------|
| s800i (Asterisk Appliance) | 1.2.x | All versions prior to |
| | | 1.3.0.3 |
+------------------------------------------------------------------------+
+------------------------------------------------------------------------+
| Corrected In |
|------------------------------------------------------------------------|
| Product | Release |
|---------------------------------------------+--------------------------|
| Asterisk Open Source | 1.2.34 |
|---------------------------------------------+--------------------------|
| Asterisk Open Source | 1.4.26.1 |
|---------------------------------------------+--------------------------|
| Asterisk Open Source | 1.6.0.12 |
|---------------------------------------------+--------------------------|
| Asterisk Open Source | 1.6.1.4 |
|---------------------------------------------+--------------------------|
| Asterisk Business Edition | B.2.5.9 |
|---------------------------------------------+--------------------------|
| Asterisk Business Edition | C.2.4.1 |
|---------------------------------------------+--------------------------|
| Asterisk Business Edition | C.3.1 |
|---------------------------------------------+--------------------------|
| s800i (Asterisk Appliance) | 1.3.0.3 |
+------------------------------------------------------------------------+
+---------------------------------------------------------------------------+
| Patches |
|---------------------------------------------------------------------------|
| Link |Branch|
|--------------------------------------------------------------------+------|
|http://downloads.digium.com/pub/security/AST-2009-005-1.2.diff.txt |1.2 |
|--------------------------------------------------------------------+------|
|http://downloads.digium.com/pub/security/AST-2009-005-1.4.diff.txt |1.4 |
|--------------------------------------------------------------------+------|
|http://downloads.digium.com/pub/security/AST-2009-005-trunk.diff.txt|trunk |
|--------------------------------------------------------------------+------|
|http://downloads.digium.com/pub/security/AST-2009-005-1.6.0.diff.txt|1.6.0 |
|--------------------------------------------------------------------+------|
|http://downloads.digium.com/pub/security/AST-2009-005-1.6.1.diff.txt|1.6.1 |
|--------------------------------------------------------------------+------|
|http://downloads.digium.com/pub/security/AST-2009-005-1.6.2.diff.txt|1.6.2 |
+---------------------------------------------------------------------------+
+------------------------------------------------------------------------+
| Links | http://labs.mudynamics.com/advisories/MU-200908-01.txt |
+------------------------------------------------------------------------+
+------------------------------------------------------------------------+
| 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-2009-005.pdf and |
| http://downloads.digium.com/pub/security/AST-2009-005.html |
+------------------------------------------------------------------------+
+------------------------------------------------------------------------+
| Revision History |
|------------------------------------------------------------------------|
| Date | Editor | Revisions Made |
|---------------------+----------------------+---------------------------|
| August 10, 2009 | Tilghman Lesher | Initial release |
+------------------------------------------------------------------------+
Asterisk Project Security Advisory - AST-2009-005
Copyright (c) 2009 Digium, Inc. All Rights Reserved.
Permission is hereby granted to distribute and publish this advisory in its
original, unaltered form.
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