CVE-2019-9970: Signal Private Messenger

Medium severity, CVSS 6.5. EPSS: 1.8% chance of exploitation in the next 30 days.

Open Whisper Signal (aka Signal-Desktop) through 1.23.1 and the Signal Private Messenger application through 4.35.3 for Android are vulnerable to an IDN homograph attack when displaying messages containing URLs. This occurs because the application produces a clickable link even if (for example) Latin and Cyrillic characters exist in the same domain name, and the available font has an identical representation of characters from different alphabets.

Affected products

• Signal Private Messenger: up to and including 4.35.3
• Signal Signal-Desktop: up to and including 1.23.1

Published 2019-03-24. Last modified 2026-06-17.