CVE-2021-27734: Belden Hirschmann Hios

Critical severity, CVSS 9.8. EPSS: 1.3% chance of exploitation in the next 30 days.

Hirschmann HiOS 07.1.01, 07.1.02, and 08.1.00 through 08.5.xx and HiSecOS 03.3.00 through 03.5.01 allow remote attackers to change the credentials of existing users.

Affected products

• Belden Hirschmann Hios: from 08.1.00, before 08.6.00 (fixed in 08.6.00); version 07.1.01 only; version 07.1.02 only
• Belden Hisecos: from 03.3.00, up to and including 03.5.01

Published 2021-05-17. Last modified 2026-06-17.