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Fencer Vulns
medium 6.7

CVE-2020-3455 json

Cisco FXOS Software for Firepower 4100/9300 Series Appliances Secure Boot Bypass Vulnerability

published 2020-10-21 6 y ago modified 2026-06-17 4 mo ago also EUVD-2020-24726

cvss
6.7
version 3.0, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 28%
public exploits
0
none known

Summary

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.

Patch / fix

  • cisco firepower_extensible_operating_system 2.4.1.268, 2.6.1.214, 2.7.1.131

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
total
Assessed
23 mo ago

Exploit prediction

0.35% chance of exploitation in the next 30 days, higher than 28% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.0 6.7 CVSS:3.0/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
NVD 3.1 7.8 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
NVD 2.0 7.2 AV:L/AC:L/Au:N/C:C/I:C/A:C

Affected products

  • Cisco Cisco Firepower Extensible Operating System (FXOS)

Classification

Weakness
  • CWE-693 Protection Mechanism Failure

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.