AST-2011-011: Possible enumeration of SIP users due to differing authentication responses

           Asterisk Project Security Advisory - AST-2011-011

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| Product | Asterisk |
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| Summary | Possible enumeration of SIP users due to |
| | differing authentication responses |
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| Nature of Advisory | Unauthorized data disclosure |
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| Susceptibility | Remote unauthenticated sessions |
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| Severity | Moderate |
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| Exploits Known | No |
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| Reported On | June 11, 2011 |
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| Reported By | |
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| Posted On | June 28, 2011 |
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| Last Updated On | June 28, 2011 |
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| Advisory Contact | Terry Wilson <[email protected]> |
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| CVE Name | CVE-2011-2536 |
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| Description | Asterisk may respond differently to SIP requests from an |
| | invalid SIP user than it does to a user configured on |
| | the system, even when the alwaysauthreject option is set |
| | in the configuration. This can leak information about |
| | what SIP users are valid on the Asterisk system. |
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| Resolution | Respond to SIP requests from invalid and valid SIP users |
| | in the same way. Asterisk 1.4 and 1.6.2 do not respond |
| | identically by default due to backward-compatibility |
| | reasons, and must have alwaysauthreject=yes set in |
| | sip.conf. Asterisk 1.8 defaults to alwaysauthreject=yes. |
| | |
| | IT IS ABSOLUTELY IMPERATIVE that users of Asterisk 1.4 |
| | and 1.6.2 set alwaysauthreject=yes in the general section |
| | of sip.conf. |
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| Links | |
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| 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| This document may be superseded by later versions; if so, the latest |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-2011-011.pdf and |
| http://downloads.digium.com/pub/security/AST-2011-011.html |
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           Asterisk Project Security Advisory - AST-2011-011
          Copyright (c) 2011 Digium, Inc. All Rights Reserved.

Permission is hereby granted to distribute and publish this advisory in its
original, unaltered form.