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

Vulnerability summary

CVE-2020-3118 is a high (CVSS 8.8) vulnerability in Cisco IOS XR. It is known to be exploited: CISA lists it, first on 03-11-2021. EPSS estimates a 11.68% chance of exploitation in the next 30 days, higher than 96% of scored vulnerabilities.

Timeline

1. 05-02-2020
   PublishedVulnerability first disclosed.
2. 03-11-2021
   Added to CISA KEVCisco IOS XR Software Discovery Protocol Format String Vulnerability
3. 03-05-2022
   CISA remediation dueApply updates per vendor instructions.
4. 21-10-2025
   Last modifiedVulnerability information updated.

Description

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).

• CWE-134Use of Externally-Controlled Format StringThe product uses a function that accepts a format string as an argument, but the format string originates from an external source.
• CWE-787Out-of-bounds WriteThe product writes data past the end, or before the beginning, of the intended buffer.