Date: 04 February 2016
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AUSCERT External Security Bulletin Redistribution
Cisco Jabber for Windows STARTTLS Downgrade Vulnerability
4 February 2016
AusCERT Security Bulletin Summary
Product: Cisco Jabber
Publisher: Cisco Systems
Operating System: Windows
Impact/Access: Access Privileged Data -- Remote/Unauthenticated
Provide Misleading Information -- Remote/Unauthenticated
CVE Names: CVE-2015-6409
Revision History: February 4 2016: Updated information about the availability of fixed releases
January 4 2016: Initial Release
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Cisco Jabber STARTTLS Downgrade Vulnerability
2016 February 3 21:33 GMT
2015 December 24 18:30 GMT
Base - 4.3
No workarounds available
Cisco Bug IDs:
A vulnerability in the Cisco Jabber client could allow an unauthenticated,
remote attacker to perform a STARTTLS downgrade attack.
The vulnerability exists because the client does not verify that an Extensible
Messaging and Presence Protocol (XMPP) connection has been established with
Transport Layer Security (TLS). An attacker could exploit this vulnerability
by performing a man-in-the-middle attack to tamper with the XMPP connection
and avoid TLS negotiation. A successful exploit could allow the attacker to
cause the client to establish a cleartext XMPP connection.
Cisco will release software updates that address this vulnerability.
Workarounds that address this vulnerability are not available.
This advisory is available at the following link:
The following table lists Cisco products that are affected by the
vulnerability that is described in this advisory.
Product Defect Fixed Release Availability
Cisco Jabber for Windows CSCux88529 11.5(1) on-premises (Available)
11.5(1) cloud (4-Feb-2016)
11.1(3) on-premises (5-Feb-2016)
11.1(3) cloud (18-Feb-2016)
10.6(7) on-premises (12-Feb-2016)
10.6(7) cloud (25-Feb-2016)
10.5(5) (18-Feb-2016 - Tentative)
9.7(7) (23-Feb-2016 - Tentative)
Cisco Jabber for Mac CSCux74900 11.5(1) on-premises (3-Feb-2016)
11.5(1) cloud (4-Feb-2016)
Cisco Jabber for Android CSCux74895 11.5(1) (Available)
Cisco Jabber for iPhone and CSCux74848 1 1.5(1) (5-Feb-2016 - Tentative)
Cisco Unified Communications CSCux80122 COP files (Available)
Manager IM & Presence Service
At the time this advisory was first published, all available releases of the
affected products, including Release 11.5(0), were vulnerable.
Products Confirmed Not Vulnerable
Voice and Video Telephony features of affected Jabber clients are not impacted
by this vulnerability as the operation of these functionalities does not rely
on the XMPP protocol.
The following products are not affected by this vulnerability:
Cisco Jabber Video for iPad
Cisco Jabber Voice for iPhone
Cisco Jabber Voice for Android
Cisco UC Integration for Microsoft Lync
Cisco Jabber Guest
Cisco Jabber Software Development Kit
No other Cisco products are currently known to be affected by this
There are no workarounds that address this vulnerability.
Please see the table in the Vulnerable Products section of this advisory for
fix availability information.
On-premise deployments will also require an update of the Cisco Unified
Communications Manager IM & Presence Service for extending protection to
When considering software upgrades, customers are advised to consult the Cisco
Security Advisories and Responses archive at http://www.cisco.com/go/psirt and
review subsequent advisories to determine exposure and a complete upgrade
In all cases, customers should ensure that the devices to upgrade contain
sufficient memory and confirm that current hardware and software
configurations will continue to be supported properly by the new release. If
the information is not clear, customers are advised to contact the Cisco
Technical Assistance Center (TAC) or their contracted maintenance providers.
Exploitation and Public Announcements
The Cisco Product Security Incident Response Team (PSIRT) is aware that
proof-of-concept exploit code is available for the vulnerability described in
this advisory. The Cisco PSIRT is not aware of any malicious exploitation of
Cisco would like to thank Renaud Dubourguais and Sbastien Dudek from Synacktiv
for discovering and reporting this vulnerability.
Version Description Section Status Date
2.1 Updated information about Affected Products - Final 2016-February-03
the availability of fixed Vulnerable Products
THIS DOCUMENT IS PROVIDED ON AN "AS IS" BASIS AND DOES NOT IMPLY ANY KIND OF
GUARANTEE OR WARRANTY, INCLUDING THE WARRANTIES OF MERCHANTABILITY OR FITNESS
FOR A PARTICULAR USE. YOUR USE OF THE INFORMATION ON THE DOCUMENT OR MATERIALS
LINKED FROM THE DOCUMENT IS AT YOUR OWN RISK. CISCO RESERVES THE RIGHT TO
CHANGE OR UPDATE THIS DOCUMENT AT ANY TIME.
A standalone copy or paraphrase of the text of this document that omits the
distribution URL is an uncontrolled copy and may lack important information or
contain factual errors. The information in this document is intended for end
users of Cisco products.
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