Overview
Visual Voice Mail (VVM) services transmit unencrypted credentials via SMS. An attacker with the ability to read SMS messages can obtain VVM IMAP credentials and gain access to VVM data.
Description
VVM is specified by Open Mobile Terminal Platform-OMPT and is implemented with SMS and IMAP (and other protocols). VVM IMAP credentials are sent unencrypted in SMS messages. From vvm-disclosure:
When a client sends any sort of STATUS SMS (activate, deactivate, status), the carrier will respond with all credentials needed to log into the IMAP server (i.e. username, password, server host-name).
From section 2.1.1.2 AUTHENTICATE of the OMTP VISUAL VOICEMAIL INTERFACE SPECIFICATION v1.3: "The IMAP4 password is sent in the STATUS SMS message."
To intercept an SMS message, an attacker would need, for example:
* temporary physical access to the SIM card,
* to operate a spoofed a base station (cell tower), or
* to convince a user to install a malicious application that has SMS access.
VVM IMAP services may be widely accessible over the internet or carrier networks.
From vvm-disclosure:
There is no indication on to a victim that someone else has access to their VVM. Android leaves their VVMs on the IMAP server until the client deletes it, so any VVMs on the client are accessible to a malicious actor.
Impact
An attacker with the ability to read SMS messages can obtain VVM IMAP credentials and gain access to VVM data.
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