Viber can access the following on your device:

In-app purchases
Device & app history

• retrieve running apps

Identity

• find accounts on the device
• add or remove accounts

Contacts

• read your contacts
• modify your contacts

Location

• approximate location (network-based)
• precise location (GPS and network-based)

SMS

• receive text messages (SMS)
• send SMS messages
• edit your text messages (SMS or MMS)
• read your text messages (SMS or MMS)

Phone

• directly call phone numbers
• read call log
• write call log

Photos/Media/Files

• modify or delete the contents of your USB storage
• read the contents of your USB storage

Camera

• take pictures and videos

Microphone

• record audio

Wi-Fi connection information

• view Wi-Fi connections

Device ID & call information

• read phone status and identity

Other

• receive data from Internet
• read sync statistics
• read your social stream
• write to your social stream
• full network access
• view network connections
• control vibration
• change your audio settings
• prevent device from sleeping
• pair with Bluetooth devices
• access Bluetooth settings
• disable your screen lock
• change network connectivity
• modify system settings
• close other apps
• set wallpaper
• create accounts and set passwords
• read sync settings
• toggle sync on and off
• send sticky broadcast
• run at startup
• draw over other apps
• use accounts on the device
• read Google service configuration

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Last Update: 06/12/2015

Source:
https://play.google.com/store/apps/details?id=com.viber.voip