CVE-2026-20281: Cisco Session Initiation Protocol SIP Software

High severity, CVSS 7.5. EPSS: 0.4% chance of exploitation in the next 30 days.

A vulnerability in Cisco Desk Phone 9800 Series, Cisco IP Phone 7800 and 8800 Series, and Cisco Video Phone 8875 that are running Cisco Session Initiation Protocol (SIP) Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. This vulnerability is due to improper memory management when an affected device processes HTTP packets. An attacker could exploit this vulnerability by sending a continuous stream of crafted HTTP packets to the device. A successful exploit could allow the attacker to cause the affected device to continuously consume memory, resulting in a DoS condition. A manual reboot of the device is required to recover from this condition. Note: For this vulnerability to be exploitable, the phone must be registered to Cisco Unified Communications Manager (Unified CM) and have Web Access enabled. Web Access is disabled by default.

Affected products

• Cisco Cisco Session Initiation Protocol SIP Software: version 12.1(1)SR1 only; version 11.5(1) only; version 10.3(2) only; version 10.2(2) only; version 10.3(1) only; version 10.3(1)SR4 only; …

Published 2026-09-02. Last modified 2026-09-02.