Security Flaw in Rakuten Viber's Cloak Mode for Android and Windows
CVE-2025-13476

9.8CRITICAL

Key Information:

Vendor

Rakuten Viber

Status
Rakuten Viber Cloak - Android
Rakuten Viber Cloak - Windows
Vendor
CVE Published:
5 March 2026

What is CVE-2025-13476?

A significant vulnerability exists in the Cloak mode of Rakuten Viber for Android and Windows, allowing the identification of proxy traffic due to a static and predictable TLS ClientHello fingerprint. This lack of extension diversity exposes users to risks from Deep Packet Inspection systems that can easily block censorship circumvention methods, thus compromising user privacy and security.

Affected Version(s)

Rakuten Viber Cloak - Android 25.7.2.0g < 27.2.0.0g

Rakuten Viber Cloak - Windows v25.6.0.0

References

https://www.viber.com/en/download/

CVSS V3.1

Score:
9.8
Severity:
CRITICAL
Confidentiality:
High
Integrity:
High
Availability:
High
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
None
User Interaction:
None
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

.