CVE-2020-3118: Cisco IOS XR Software Discovery Protocol Format String Vulnerability

CISA Known Exploited Vulnerabilities

Name

Cisco IOS XR Software Discovery Protocol Format String Vulnerability

Vendor

Cisco

Product

IOS XR

Added to the catalog

2021-11-03

Due date for US federal agencies

2022-05-03

Weaknesses

CWE-134

Catalog version

2026.10.30

Cisco IOS XR improperly validates string input from certain fields in Cisco Discovery Protocol messages. Exploitation could allow an unauthenticated, adjacent attacker to execute code with administrative privileges or cause a reload on an affected device.

Required action (CISA)

Apply updates per vendor instructions.

Ransomware use: CISA does not mark known use of this vulnerability in ransomware campaigns.

Links in CISA's notes

• https://nvd.nist.gov/vuln/detail/CVE-2020-3118

Read on 2026-11-02T23:39:54.475Z under licence cisa-kev-cc0@b0067899 from https://www.cisa.gov/sites/default/files/feeds/known_exploited_vulnerabilities.json

NVD analysis

Status

Analyzed

Published

2020-02-05T18:15:10.907

Last modified

2026-06-17T03:17:23.013

Weaknesses

CWE-134, CWE-787

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).

References

• http://packetstormsecurity.com/files/156203/Cisco-Discovery-Protocol-CDP-Remote-Device-Takeover.html (Third Party Advisory, VDB Entry)
• https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20200205-iosxr-cdp-rce (Vendor Advisory)
• http://packetstormsecurity.com/files/156203/Cisco-Discovery-Protocol-CDP-Remote-Device-Takeover.html (Third Party Advisory, VDB Entry)
• https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20200205-iosxr-cdp-rce (Vendor Advisory)
• https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2020-3118 (US Government Resource)

This product uses the NVD API but is not endorsed or certified by the NVD.

Read on 2026-11-02T23:41:43.468Z under licence nvd-api-terms-of-use@ff2a5288 from https://services.nvd.nist.gov/rest/json/cves/2.0?cveId=CVE-2020-3118

CVE record

Title (CNA)

Cisco IOS XR Software Cisco Discovery Protocol Format String Vulnerability

Assigner

cisco

State

PUBLISHED

Published

2020-02-05T17:40:16.080Z

Updated

2025-10-21T23:35:52.708Z

Problem types

CWE-134

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).

References

• 20200205 Cisco IOS XR Software Cisco Discovery Protocol Format String Vulnerability
• http://packetstormsecurity.com/files/156203/Cisco-Discovery-Protocol-CDP-Remote-Device-Takeover.html

Read on 2026-11-03T01:04:22.564Z under licence cve-terms-of-use@81bfa2f3 from https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2020/3xxx/CVE-2020-3118.json

Defensive techniques (MITRE D3FEND)

D3FEND maps these defensive techniques to the weakness (CWE) that NVD lists for this CVE, through the digital artifacts the weakness affects. D3FEND does not say they stop this vulnerability.

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