Open-Xchange Security Advisory 2013-07-31

[Martin Braun <martin.braun@xxxxxxxxxxxxxxxx>]

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@xxxxxxxxxxxxxxx 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@xxxxxxxxxxxxxxx" 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.