CVE-2015-6391: Cisco Unified SIP Phone 3900 Firmware

High severity, CVSS 7.8. EPSS: 1.9% chance of exploitation in the next 30 days.

Cisco Unified SIP 3905 phones allow remote attackers to cause a denial of service (resource consumption and functionality loss) via a large amount of network traffic, aka Bug ID CSCuh51331.

Affected products

• Cisco Unified SIP Phone 3900 Firmware: version 8.1(1b) only; version 8.1(2) only; version 8.1(2)sr1 only; version 8.1(3) only; version 8.1(4) only; version 9.2(1) only; …

Published 2015-12-05. Last modified 2026-06-17.