Title: Privilege Escalation
Product: Emerson Smart Wireless Gateway
Vendor Homepage: http://emerson.com
Vulnerable Version: 1420 4.6.59
CVE Number: CVE-2020-19417
Authors: Harsha Bhat Anish Mitra and Unmesh Guragol
Timeline:
2019-08-02 Disclosed to the vendor
2019-08-22 Vendor confirmed that the vulnerability was identified
internally and a fix was released in the latest version of firmware

1. Vulnerability Description

Emerson Smart Wireless Gateway 1420 4.6.59 allows non-privileged users
(such as the default account 'maint') to perform administrative tasks by
sending specially crafted HTTP requests to the application.

2. PoC

The PoC explained below is to perform an action accessible ideally only to
an 'administrator' account
Step 1: Using a proxy tool such as Burp Suite, capture an original request
that sets the login banner on the device from a legitimate 'administrator'
account.
Step 2: Logout from the application and login with a low privilege user
account such as 'maint'. This account does not have privileges to set the
login banner.
Step 3: Replay the original request from 'Step 1' after replacing session
ID of 'administrator' account to that of 'maint' account.

Observe that the application, without validating the permissions set for
'maint' account sets the login banner via the low-privilege account.


3. Solution

The vendor provides an updated version of firmware which should be
installed immediately.

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