CVE-2020-3524: Cisco IOS XE ROM Monitor Software Vulnerability

Severity: medium (CVSS 6.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2020-09-24 · updated 2026-06-17
Weakness: CWE-284

Description

A vulnerability in the Cisco IOS XE ROM Monitor (ROMMON) Software for Cisco 4000 Series Integrated Services Routers, Cisco ASR 920 Series Aggregation Services Routers, Cisco ASR 1000 Series Aggregation Services Routers, and Cisco cBR-8 Converged Broadband Routers could allow an unauthenticated, physical attacker to break the chain of trust and load a compromised software image on an affected device. The vulnerability is due to the presence of a debugging configuration option in the affected software. An attacker could exploit this vulnerability by connecting to an affected device through the console, forcing the device into ROMMON mode, and writing a malicious pattern using that specific option on the device. A successful exploit could allow the attacker to break the chain of trust and load a compromised software image on the affected device. A compromised software image is any software image that has not been digitally signed by Cisco.

Affected products

Cisco IOS XE ROMMON Software: before 16.2\(1r\); before 15.6\(18r\); before 16.4\(1r\)s — fixed in 15.6\(18r\), 16.2\(1r\), 16.4\(1r\)s

How to fix

Upgrade to a fixed version: Cisco IOS XE ROMMON Software 15.6\(18r\), 16.2\(1r\), 16.4\(1r\)s. Check the vendor advisory for mitigations.

References

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