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

Source: https://junglewise.ai/threats/cve-2020-3118-cisco-ios-xr-software-discovery-protocol-format-string  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2021-11-03. Updated: 2026-05-10  
License: CC BY 4.0 with a link back

CVE-2020-3118 · Severity: critical · CVSS 8.8 · Exploited in the wild · Published 2021-11-03

A format string vulnerability in the Cisco Discovery Protocol (CDP) implementation of Cisco IOS XR Software allows an unauthenticated, adjacent attacker to execute arbitrary code with administrative privileges or cause a device reload. The flaw exists due to improper validation of string input in certain CDP message fields, which can lead to a stack overflow.

Technologies: [Cisco IOS XR](https://junglewise.ai/threats/technologies/ios-xr). Vendors: [Cisco](https://junglewise.ai/threats/vendors/cisco).

## Quick answers

**Is CVE-2020-3118 exploited in the wild?** Yes. CVE-2020-3118 is known to be exploited in the wild, first recorded on 3 November 2021. Treat it as urgent.

**How severe is CVE-2020-3118?** Critical severity, with a CVSS score of 8.8, published 3 November 2021.

**Which products and versions are affected?** Cisco IOS XR Software 5.2.5, 6.4.2, 6.5.2, 6.5.3.

**Is there a fix for CVE-2020-3118?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2020-3118 attacked?** It is attacked from the adjacent network, in an operating system.

**Am I affected by CVE-2020-3118?** Check whether you run Cisco IOS XR. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Affected products

- Cisco IOS XR Software 5.2.5, 6.4.2, 6.5.2, 6.5.3

## Timeline

- 2020-02-05: advisory: Initial vendor advisory published by Cisco
- 2021-11-03: kev added: Added to CISA Known Exploited Vulnerabilities Catalog
- 2021-11-03: disclosed

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