---
id: "CVE-2020-3118"
kind: "vulnerability"
aliases: ["CVE-2020-3118"]
title: "Cisco IOS XR: Cisco IOS XR Software Discovery Protocol Format String Vulnerability"
severity: "high"
cvss: 8.8
epss: 0.11685
exploited: true
status: "open"
category: "infrastructure"
products: [{"name": "Cisco IOS XR", "fixed": [], "affected": "", "ecosystem": "vendor"}]
ecosystems: ["vendor"]
tags: ["cisco", "exploited", "infrastructure", "ios-xr", "network-devices"]
not_affected_if: ["cdp-disabled", "no-ios-xr"]
published_at: "2020-02-05T18:15:10+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-2020-3118", "first_seen_at": "2026-10-23T19:11:53+00:00"}, {"source": "epss", "url": "https://api.first.org/data/v1/epss?cve=CVE-2020-3118", "first_seen_at": "2026-10-23T19:13:44+00:00"}, {"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2020-3118", "first_seen_at": "2026-10-23T21:57:35+00:00"}]
---

# Cisco IOS XR: Cisco IOS XR Software Discovery Protocol Format String Vulnerability

Cisco IOS XR network devices improperly validate string fields in Cisco Discovery Protocol messages, which causes a format string flaw. An unauthenticated attacker on the same network segment can run code with administrative privileges or force the device to reload.

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

## Affected

- vendor:Cisco IOS XR affected ? fixed ?

## Fix

Apply the update per Cisco's vendor advisory; the sources do not name the fixed IOS XR versions.

## Timeline

- 2026-10-23T19:11:53+00:00 kev https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2020-3118
- 2026-10-23T19:13:44+00:00 epss https://api.first.org/data/v1/epss?cve=CVE-2020-3118
- 2026-10-23T21:57:35+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2020-3118

## From the sources

A vulnerability in the Cisco Discovery Protocol implementation for Cisco IOS XR Software could allow an unauthenticated, adjacent attacker to execute arbitrary code or cause a reload on an affected device. The vulnerability is due to improper validation of string input from certain fields in Cisco Discovery Protocol messages. An attacker could exploit this vulnerability by sending a malicious Cisco Discovery Protocol packet to an affected device. A successful exploit could allow the attacker to cause a stack overflow, which could allow the attacker to execute arbitrary code with administrative privileges on an affected device. Cisco Discovery Protocol is a Layer 2 protocol. To exploit this vulnerability, an attacker must be in the same broadcast domain as the affected device (Layer 2 adjacent).

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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_