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Cisco IOS XE Software for Catalyst Rugged Series Switches Secure Boot Bypass (cisco-sa-xe-secureboot-bypass-B6uYxYSZ)

medium Nessus Plugin ID 303633

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Synopsis

The remote device is missing a vendor-supplied security patch

Description

According to its self-reported version, Cisco IOS-XE Software is affected by a vulnerability.

 - A vulnerability in the bootloader of Cisco IOS XE Software for Cisco Catalyst 9200 Series Switches, Cisco Catalyst ESS9300 Embedded Series Switches, Cisco Catalyst IE9310 and IE9320 Rugged Series Switches, and Cisco IE3500 and IE3505 Rugged Series Switches could allow an authenticated, local attacker with level-15 privileges or an unauthenticated attacker with physical access to an affected device to execute arbitrary code at boot time and break the chain of trust. This vulnerability is due to insufficient validation of software at boot time. An attacker could exploit this vulnerability by manipulating the loaded binaries on an affected device to bypass some of the integrity checks that are performed during the boot process. A successful exploit could allow the attacker to execute code that bypasses the requirement to run Cisco- signed images. Cisco has assigned this security advisory a Security Impact Rating (SIR) of High rather than Medium as the score indicates because this vulnerability allows an attacker to bypass a major security feature of a device. (CVE-2026-20104)

Please see the included Cisco BIDs and Cisco Security Advisory for more information.

Solution

Upgrade to the relevant fixed version referenced in Cisco bug IDs CSCwr77016, CSCws75667

See Also

https://bst.cloudapps.cisco.com/bugsearch/bug/CSCwr77016

https://bst.cloudapps.cisco.com/bugsearch/bug/CSCws75667

http://www.nessus.org/u?7cd472c8

http://www.nessus.org/u?b40d902b

Plugin Details

Severity: Medium

ID: 303633

File Name: cisco-sa-xe-secureboot-bypass-B6uYxYSZ-iosxe.nasl

Version: 1.3

Type: Combined

Family: CISCO

Published: 3/25/2026

Updated: 7/8/2026

Supported Sensors: Nessus

Risk Information

VPR

Risk Factor: Medium

Score: 4.3

Percentile: 53.26

CVSS v2

Risk Factor: Medium

Base Score: 6.6

Temporal Score: 4.9

Vector: CVSS2#AV:L/AC:L/Au:N/C:C/I:C/A:N

CVSS Score Source: CVE-2026-20104

CVSS v3

Risk Factor: Medium

Base Score: 6.1

Temporal Score: 5.3

Vector: CVSS:3.0/AV:P/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

Temporal Vector: CVSS:3.0/E:U/RL:O/RC:C

Vulnerability Information

CPE: cpe:/o:cisco:ios_xe

Required KB Items: Host/Cisco/IOS-XE/Version, Host/Cisco/IOS-XE/Model

Exploit Ease: No known exploits are available

Patch Publication Date: 3/25/2026

Vulnerability Publication Date: 3/25/2026

Reference Information

CVE: CVE-2026-20104

CWE: 124

CISCO-SA: cisco-sa-xe-secureboot-bypass-B6uYxYSZ

IAVA: 2026-A-0263

CISCO-BUG-ID: CSCwr77016, CSCws75667