---
id: "CVE-2020-3161"
kind: "vulnerability"
aliases: ["CVE-2020-3161"]
title: "Cisco Cisco IP Phones: Cisco IP Phones Web Server Remote Code Execution and Denial-of-Service Vulnerability"
severity: "critical"
cvss: 10.0
epss: 0.83855
exploited: true
status: "open"
category: "infrastructure"
products: [{"name": "Cisco Cisco IP Phones", "fixed": [], "affected": "", "ecosystem": "vendor"}]
ecosystems: ["vendor"]
tags: ["cisco", "exploited", "infrastructure", "ip-phones", "voip"]
not_affected_if: ["unknown"]
published_at: "2020-04-15T20:15:15+00:00"
first_seen_at: "2026-10-23T19:11:53+00:00"
updated_at: "2026-10-23T21:57:35+00:00"
sources: [{"source": "kev", "url": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2020-3161", "first_seen_at": "2026-10-23T19:11:53+00:00"}, {"source": "epss", "url": "https://api.first.org/data/v1/epss?cve=CVE-2020-3161", "first_seen_at": "2026-10-23T19:13:44+00:00"}, {"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2020-3161", "first_seen_at": "2026-10-23T21:57:35+00:00"}]
---

# Cisco Cisco IP Phones: Cisco IP Phones Web Server Remote Code Execution and Denial-of-Service Vulnerability

Cisco IP Phones have an input validation flaw in their web server that accepts crafted HTTP requests. An unauthenticated attacker can run code remotely with root privileges or crash the phone's web service.

_Summary, check and fix written by a model from the sources; labelled as such._

## Affected

- vendor:Cisco Cisco IP Phones affected ? fixed ?

## How to check

Identify affected Cisco IP Phone models and firmware versions from the Cisco advisory; the sources do not give a check command.

## Fix

Apply the Cisco firmware update for the affected phone models per vendor instructions; the sources do not name the fixed version.

## Timeline

- 2026-10-23T19:11:53+00:00 kev https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2020-3161
- 2026-10-23T19:13:44+00:00 epss https://api.first.org/data/v1/epss?cve=CVE-2020-3161
- 2026-10-23T21:57:35+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2020-3161

## From the sources

A vulnerability in the web server for Cisco IP Phones could allow an unauthenticated, remote attacker to execute code with root privileges or cause a reload of an affected IP phone, resulting in a denial of service (DoS) condition. The vulnerability is due to a lack of proper input validation of HTTP requests. An attacker could exploit this vulnerability by sending a crafted HTTP request to the web server of a targeted device. A successful exploit could allow the attacker to remotely execute code with root privileges or cause a reload of an affected IP phone, resulting in a DoS condition.

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_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_