CVE-2020-3574: Cisco IP Phone TCP Packet Flood Denial of Service Vulnerability

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 8.0% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2020-11-06 · updated 2026-06-17
Weakness: CWE-371

Description

A vulnerability in the TCP packet processing functionality of Cisco IP Phones could allow an unauthenticated, remote attacker to cause the phone to stop responding to incoming calls, drop connected calls, or unexpectedly reload. The vulnerability is due to insufficient TCP ingress packet rate limiting. An attacker could exploit this vulnerability by sending a high and sustained rate of crafted TCP traffic to the targeted device. A successful exploit could allow the attacker to impact operations of the phone or cause the phone to reload, leading to a denial of service (DoS) condition.

Affected products

Cisco Ip Dect 210 Firmware: before 4.8.1 — fixed in 4.8.1
Cisco Ip Dect 6825 Firmware: before 4.8.1 — fixed in 4.8.1
Cisco Ip Phone 8811 Firmware: before 11.3.2 — fixed in 11.3.2
Cisco Ip Phone 8841 Firmware: before 11.3.2 — fixed in 11.3.2
Cisco Ip Phone 8851 Firmware: before 11.3.2 — fixed in 11.3.2
Cisco Ip Phone 8861 Firmware: before 11.3.2 — fixed in 11.3.2
Cisco Unified Ip Conference Phone 8831 Firmware: 9.3(4)-servicerelease3
Cisco Webex Room Phone Firmware: before 1.2.0 — fixed in 1.2.0

How to fix

Upgrade to a fixed version: Cisco Ip Dect 210 Firmware 4.8.1; Cisco Ip Dect 6825 Firmware 4.8.1; Cisco Ip Phone 8811 Firmware 11.3.2; Cisco Ip Phone 8841 Firmware 11.3.2; Cisco Ip Phone 8851 Firmware 11.3.2; Cisco Ip Phone 8861 Firmware 11.3.2; Cisco Webex Room Phone Firmware 1.2.0. Check the vendor advisory for mitigations.

References

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