Open-Xchange Security Advisory 2013-07-31

[Martin Braun <martin.braun () open-xchange com>]

Product: Open-Xchange AppSuite
Vendor: Open-Xchange GmbH

Internal reference: 27473 (Bug ID)
Vulnerability type: Phishing / Data injection
Vulnerable version: 7.2.2 and earlier
Vulnerable component: backend
Fixed version: 7.2.2-rev9, 7.2.1-rev10, 7.2.0-rev11, 7.0.2-rev14
Solution status: Fixed by Vendor
Vendor notification: 2013-07-11
Solution date: 2013-07-18
Public disclosure: 2013-07-31
CVE reference: CVE-2013-4790
CVSSv2: 5.1 (AV:N/AC:M/Au:S/C:P/I:N/A:N/E:U/RL:U/RC:C/CDP:LM/TD:H/CR:ND/IR:ND/AR:ND)

Vulnerability Details:
To provide easy integration of third party mail accounts, Open-Xchange uses several auto-discovery features. Besides a 
generic lookup for most prominent mail providers, information of existing external mail accounts of other users, 
including users from other contexts, is used to discover potential mail server settings. To validate the discovered 
settings, a login attempt is performed at the discovered mail server. This attack becomes possible if the victim is 
using OX AppSuite UI, using the OX6 UI does not trigger this vulnerability.

Risk:
An attacker can inject incorrect host information for popular mail services by providing misleading server settings. 
These settings are then used to automatically validate other users external mail accounts which includes transferring 
their external mail accounts login name and password. An attacker can potentially intercept user credentials for 
external mail accounts by logging all authentication data sent to the rogue IMAP server.

Steps to reproduce:
As User A (attacker)
1. Login
2. Switch to Settings -> Mail and Social accounts
3. Add a new mail account, use "manual mode"
4. Enter foo () my-mail-host io as mail address, the attackers evil IMAP servers IP or hostname as server name and 
provide valid credentials for that evil server
5. Save the account

As User B (victim)
1. Login
2. Switch to Settings -> Mail and Social accounts
3. Add a new mail account, use "automatic mode"
4. Enter "bar () my-mail-host io" as address and provide your password
5. Save

Proof of concept:
A login request is performed at the evil IMAP server, not at the domain related to the entered mail address.

92.224.190.xxx = OX server
37.235.49.xxx = Evil IMAP server

#
T 92.224.190.xxx:40622 -> 37.235.49.xxx:143 [A]
  .F#...7......(..}.....hK..%...N..{dp..."45._r.....4>......v.​.Zs8...C(..D.I.V..3..YboF......                          
                                                                                                                        
                                       
######
T 37.235.49.xxx:143 -> 92.224.190.xxx:47458 [AP]
  * OK [CAPABILITY IMAP4rev1 LITERAL+ SASL-IR LOGIN-REFERRALS ID ENABLE STARTTLS LOGINDISABLED] Dovecot ready...        
                                
##
T 92.224.190.xxx:47458 -> 37.235.49.xxx:143 [AP]
  A11 LOGOUT.. 


Solution:
Users should update to the latest available patch releases 7.2.2-rev9, 7.2.1-rev10, 7.2.0-rev11, 7.0.2-rev14.