CVE-2020-3455
Cisco FXOS Software for Firepower 4100/9300 Series Appliances Secure Boot Bypass Vulnerability
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.
Attack profile
How easy it is to exploit
- Attack vector
- Local
- Complexity
- Low
- Privileges needed
- High
- User interaction
- None
What an attacker can affect
- Confidentiality
- High
- Integrity
- High
- Availability
- High
Exploit likelihood
What each source reports
CVE List Score used
6.7
Cisco FXOS Software for Firepower 4100/9300 Series Appliances Secure Boot Bypass Vulnerability
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.
- Record
CVE-2020-3455- CVSS 3.0
- 6.7 Medium
CVSS:3.0/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H - Weakness
- CWE-693
- Updated
- 2026-11-02
EUVDEUVD-2020-24726
6.7
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.
- Record
EUVD-2020-24726- CVSS 3.0
- 6.7 Medium
CVSS:3.0/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H - Updated
- 2026-11-03
GitHub AdvisoriesGHSA-4c77-wcw2-9gh7 No score
A vulnerability in the secure boot process of Cisco FXOS Software could allow an authenticated,...
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.
- Record
GHSA-4c77-wcw2-9gh7- Updated
- 2026-11-02
NVD
7.8
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.
- Record
CVE-2020-3455- CVSS 3.1
- 7.8 High
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H - CVSS 3.0
- 6.7 Medium
CVSS:3.0/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H - CVSS 2.0
- 7.2 High
AV:L/AC:L/Au:N/C:C/I:C/A:C - Weakness
- CWE-693
- Updated
- 2026-11-02
Affected products
History
| Recorded | Changed | Sources |
|---|---|---|
| aliases, published | EUVD | |
| first indexed | CVE List, GitHub Advisories, NVD |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2020-3455 is a medium vulnerability (CVSS 6.7) in Cisco Firepower Extensible Operating System (fxos), published October 21, 2020. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.35%, the 28th percentile. No source names a fixed version.