Asterisk Project Security Advisory - An attacker may request an Asterisk server to send part of a firmware image. However, as this firmware download protocol does not initiate a handshake, the source address may be spoofed. Therefore, an IAX2 FWDOWNL request for a firmware file may consume as little as 40 bytes, yet produces a 1040 byte response. Coupled with multiple geographically diverse Asterisk servers, an attacker may flood an victim site with unwanted firmware packets.
033fd05fff387ab0474d5a49f0a057699dcb0943d8893658905cf254d19d1aa2 Asterisk Project Security Advisory - AST-2008-011
+------------------------------------------------------------------------+
| Product | Asterisk |
|--------------------+---------------------------------------------------|
| Summary | Traffic amplification in IAX2 firmware |
| | provisioning system |
|--------------------+---------------------------------------------------|
| Nature of Advisory | Traffic amplification attack |
|--------------------+---------------------------------------------------|
| Susceptibility | Remote unauthenticated sessions |
|--------------------+---------------------------------------------------|
| Severity | Critical |
|--------------------+---------------------------------------------------|
| Exploits Known | No |
|--------------------+---------------------------------------------------|
| Reported On | July 18, 2008 |
|--------------------+---------------------------------------------------|
| Reported By | Tilghman Lesher < tlesher AT digium DOT com > |
|--------------------+---------------------------------------------------|
| Posted On | July 22, 2008 |
|--------------------+---------------------------------------------------|
| Last Updated On | July 22, 2008 |
|--------------------+---------------------------------------------------|
| Advisory Contact | Tilghman Lesher < tlesher AT digium DOT com > |
|--------------------+---------------------------------------------------|
| CVE Name | CVE-2008-3264 |
+------------------------------------------------------------------------+
+------------------------------------------------------------------------+
| Description | An attacker may request an Asterisk server to send part |
| | of a firmware image. However, as this firmware download |
| | protocol does not initiate a handshake, the source |
| | address may be spoofed. Therefore, an IAX2 FWDOWNL |
| | request for a firmware file may consume as little as 40 |
| | bytes, yet produces a 1040 byte response. Coupled with |
| | multiple geographically diverse Asterisk servers, an |
| | attacker may flood an victim site with unwanted firmware |
| | packets. |
+------------------------------------------------------------------------+
+------------------------------------------------------------------------+
| Workaround | The only device which used this firmware upgrade |
| | procedure was the IAXy ATA device, and the last firmware |
| | upgrade was more than 18 months ago. It is unlikely that |
| | any IAXy devices in use today still need the last |
| | firmware upgrade. Therefore, deleting the firmware image |
| | from the directory where it is served from and sending a |
| | reload event to the Asterisk server is sufficient to |
| | purge the firmware image from the Asterisk server's |
| | memory. An Asterisk server which is unable to serve out |
| | the requested firmware image will reply to any such |
| | request with a much smaller REJECT packet, which is |
| | smaller than even the FWDOWNL packet. |
+------------------------------------------------------------------------+
+------------------------------------------------------------------------+
| Resolution | This firmware download procedure has been disabled by |
| | default in Asterisk. If you should still need to upgrade |
| | IAXys in the field, there is an option 'allowfwdownload' |
| | which can be enabled. However, due to the reasons |
| | specified on the Workaround section, it is recommended |
| | that you leave this option disabled and enable it only on |
| | secure internal networks when an IAXy is initially |
| | provisioned. |
+------------------------------------------------------------------------+
+------------------------------------------------------------------------+
| Affected Versions |
|------------------------------------------------------------------------|
| Product | Release | |
| | Series | |
|----------------------------------+-------------+-----------------------|
| Asterisk Open Source | 1.0.x | All versions |
|----------------------------------+-------------+-----------------------|
| Asterisk Open Source | 1.2.x | All versions prior to |
| | | 1.2.30 |
|----------------------------------+-------------+-----------------------|
| Asterisk Open Source | 1.4.x | All versions prior to |
| | | 1.4.21.2 |
|----------------------------------+-------------+-----------------------|
| Asterisk Addons | 1.2.x | Not affected |
|----------------------------------+-------------+-----------------------|
| Asterisk Addons | 1.4.x | Not affected |
|----------------------------------+-------------+-----------------------|
| Asterisk Business Edition | A.x.x | All versions |
|----------------------------------+-------------+-----------------------|
| Asterisk Business Edition | B.x.x | All versions prior to |
| | | B.2.5.4 |
|----------------------------------+-------------+-----------------------|
| Asterisk Business Edition | C.x.x | All versions prior to |
| | | C.1.10.3 |
|----------------------------------+-------------+-----------------------|
| AsteriskNOW | pre-release | All versions |
|----------------------------------+-------------+-----------------------|
| Asterisk Appliance Developer Kit | 0.x.x | All versions |
|----------------------------------+-------------+-----------------------|
| s800i (Asterisk Appliance) | 1.0.x | All versions prior to |
| | | 1.2.0.1 |
+------------------------------------------------------------------------+
+------------------------------------------------------------------------+
| Corrected In |
|------------------------------------------------------------------------|
| Product | Release |
|---------------------------------------------+--------------------------|
| Asterisk Open Source | 1.2.30 |
|---------------------------------------------+--------------------------|
| Asterisk Open Source | 1.4.21.2 |
|---------------------------------------------+--------------------------|
| Asterisk Business Edition | B.2.5.4 |
|---------------------------------------------+--------------------------|
| Asterisk Business Edition | C.1.10.3 |
|---------------------------------------------+--------------------------|
| Asterisk Business Edition | C.2.0.3 |
|---------------------------------------------+--------------------------|
| s800i (Asterisk Appliance) | 1.2.0.1 |
+------------------------------------------------------------------------+
+------------------------------------------------------------------------+
| Links | |
+------------------------------------------------------------------------+
+------------------------------------------------------------------------+
| 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-2008-011.pdf and |
| http://downloads.digium.com/pub/security/AST-2008-011.html |
+------------------------------------------------------------------------+
+------------------------------------------------------------------------+
| Revision History |
|------------------------------------------------------------------------|
| Date | Editor | Revisions Made |
|-----------------+--------------------+---------------------------------|
| July 22, 2008 | Tilghman Lesher | Initial release |
|-----------------+--------------------+---------------------------------|
| July 22, 2008 | Tilghman Lesher | Revised C.1 version numbers |
+------------------------------------------------------------------------+
Asterisk Project Security Advisory - AST-2008-011
Copyright (c) 2008 Digium, Inc. All Rights Reserved.
Permission is hereby granted to distribute and publish this advisory in its
original, unaltered form.
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