CVE-2026-20104

mediumpriority · track · 0EPSS 0.002 · 5 %ileDEEUNLRUUS
grimoire priorityP3 · Track
Exploitable?
—
no known exploitation
Likely / severe?
0.16% (5th) EPSS
CVSS 6.1 · medium
Is it mine?
258 products
Check your exposure
Who says so?
6 sources
cnnvd · enisa_euvd · fstec_bdu · cert_bund

EPSS · scored 2026-10-26

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.

01

remediations

Vendor fix, mitigation, or workaround guidance, as published by each source.

A vendor fix is available.

02

cvss

Technical severity, 0–10. One row per scoring source.

6.1
010

base score 0–10 · higher = more severe · hover a vector to decode

v3.16.1mediumAV:P/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:Nsecondary · FSTEC (BDU) RU
v3.16.1mediumCVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:Nsecondary · ENISA EU
v3.16.1mediumCVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:Nsecondary · psirt@cisco.com USexploitability 0.9 · impact 5.2
v3.15.6mediumCVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N/E:Usecondary · CVSS-BT (t0sche)
v3.16.1mediumCVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:Nsecondary · NCSC-NL NL
v3.16.1mediumCVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:Nsecondary · Cisco PSIRT US
03

ssvc

A stakeholder decision — act, attend, or track — from exploitation and impact.

Exploitation: none · Automatable: no · Technical Impact: totalcoordinatorcisa_ssvcUS
04

weaknesses

The CWE weakness classes this flaw belongs to.

CWE-124USCWE-124USCWE-124US
05

affected products (258)

Products and version ranges known to be affected.

showing 20 of 258
06

advisories (3)

Vendor and ecosystem advisories describing this.

  • NCSC-2026-0104Kwetsbaarheden verholpen in Cisco IOS XE SoftwareNL2026-03-26csaf · ncsc_nlNL

    Cisco heeft kwetsbaarheden verholpen in Cisco IOS XE Software, specifiek voor verschillende producten zoals Catalyst 9000 Series Switches, Catalyst CW9800 Family, en Cisco Meraki.

  • WID-SEC-W-2026-0874Cisco IOS und IOS XE Software: Mehrere SchwachstellenDeutsch2026-03-25csaf · cert_bundDE

    Ein Angreifer kann mehrere Schwachstellen in Cisco IOS XE, Cisco IOS und Cisco Catalyst ausnutzen, um sich erweiterte Rechte zu verschaffen, beliebigen Code auszuführen, Sicherheitsmaßnahmen zu umgehen, Cross-Site-Scripting-Angriffe durchzuführen, Daten zu manipulieren, vertrauliche Informationen offenzulegen und einen Denial-of-Service-Zustand herbeizuführen.

  • cisco-sa-xe-secureboot-bypass-B6uYxYSZCisco IOS XE Software for Cisco Catalyst and Rugged Series Switches Secure Boot Bypass Vulnerability2026-03-25csaf · cisco_csafUS

    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. Cisco has released software updates that address this vulnerability. There are no workarounds that address this vulnerability. This advisory is part of the March 2026 release of the Cisco IOS and IOS XE Software Security Advisory Bundled Publication. For a complete list of the advisories and links to them, see Cisco Event Response: March 2026 Semiannual Cisco IOS and IOS XE Software Security Advisory Bundled Publication ["https://sec.cloudapps.cisco.com/security/center/viewErp.x?alertId=ERP-75297"].

07

also known as (4)

Other names and identifiers for this entity.

08

sources

Which sources assert this record, and when.

cnnvdenisa_euvdfstec_bducert_bundcisco_csafncsc_nlNVDCVE.orgMITRE
published 2026-03-25modified 2026-09-28
09

references (4)

External citations — patches, advisories, analysis.

scry

Attackers weaponise vulnerabilities like this against internet-exposed services. See what is exposed on your perimeter with a free passive scan.

Free scan