Viber for Windows up to 13.2.0.39 does not properly quote its custom URI handler. A malicious website could launch Viber with arbitrary parameters, forcing a victim to send an NTLM authentication request, and either relay the request or capture the hash for offline password cracking. NOTE: this issue exists because of an incomplete fix for CVE-2019-12569.

A vulnerability in Viber before 10.7.0 for Desktop (Windows) could allow an attacker to execute arbitrary commands on a targeted system. This vulnerability is due to unsafe search paths used by the application URI. An attacker could exploit this vulnerability by convincing a targeted user to follow a malicious link. Successful exploitation could cause the application to load libraries from the directory targeted by the URI link. The attacker could use this behavior to execute arbitrary commands on the system with the privileges of the targeted user, if the attacker can place a crafted library in a directory that is accessible to the vulnerable system.