CVE-2020-3455: Cisco FXOS Software for Firepower 4100/9300 Series Appliances Secure Boot Bypass Vulnerability

Severity: high (CVSS 7.8 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: 2020-10-21 · updated 2026-06-17
Weakness: CWE-693

Description

A vulnerability in the secure boot process of Cisco FXOS Software could allow an authenticated, local attacker to bypass the secure boot mechanisms. The vulnerability is due to insufficient protections of the secure boot process. An attacker could exploit this vulnerability by injecting code into a specific file that is then referenced during the device boot process. A successful exploit could allow the attacker to break the chain of trust and inject code into the boot process of the device which would be executed at each boot and maintain persistence across reboots.

Affected products

Cisco Firepower Extensible Operating System (FXOS): before 2.4.1.268; from 2.6 before 2.6.1.214; from 2.7 before 2.7.1.131 — fixed in 2.4.1.268, 2.6.1.214, 2.7.1.131

How to fix

Upgrade to a fixed version: Cisco Firepower Extensible Operating System (FXOS) 2.4.1.268, 2.6.1.214, 2.7.1.131. Check the vendor advisory for mitigations.

References

Get alerted when CVE-2020-3455 or the next vulnerability affects your stack