Medium6.1Vendor: HighCisco

Medium [CVE-2026-20104] Cisco IOS XE Software for Cisco Catalyst and Rugged Series Switches Secure Boot Bypass Vulnerability

This medium-severity Cisco advisory covers CVE-2026-20104 affecting Cisco IOS XE Software 16.12.8, Cisco IOS XE Software 16.12.6a, Cisco IOS XE Software 16.12.7.

cisco-sa-xe-secureboot-bypass-B6uYxYSZ Published Mar 25, 2026Updated by vendor Mar 25, 2026

CVE-2026-20104

Affected products & platforms

CiscoSwitchesCatalystIOS XECatalyst 9200

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Summary

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 …

Affected products named by the advisory: Cisco IOS XE Software 16.12.8; Cisco IOS XE Software 16.12.6a; Cisco IOS XE Software 16.12.7; Cisco IOS XE Software 17.3.3; and 3 more.

Affected versions

Scope: This vulnerability affects the following Cisco products if they are running a vulnerable release of Cisco IOS XE Software, regardless of device configuration:

Official advisory · high-confidence parse· fetched 2 months ago·verify at source

Fixed versions

No fixed release is recorded yet. That does not prove no patch exists — confirm against the vendor advisory.

Official advisory · high-confidence parse· fetched 2 months ago·verify at source

Mitigation checklist

Workaround status

There are no workarounds that address this vulnerability.

Official advisory · high-confidence parse· fetched 2 months ago·verify at source

Sources

Official and corroborating records used to build this advisory.

Cisco Security Advisories (PSIRT)official
Official vendor feed — the source of truth for this advisory. VulniPulse polled this feed and parsed this entry from it. Discovered from the machine-readable feed https://sec.cloudapps.cisco.com/security/center/psirtrss20/CiscoSecurityAdvisory.xml; this link opens the Cisco advisory index instead of the raw feed document.
Cisco
Vendor advisory pageofficial
Advisory page fetched and parsed to extract affected/fixed versions and mitigation guidance beyond what the feed carries.
Cisco

Cross-references

Validate CVE metadata against the authoritative registries.

CVE-2026-20104NVD CVE.org MITRE

Official resources

Cisco Catalyst switch software upgrade guide
Official documentation
Official upgrade documentation for Cisco Catalyst campus switches (IOS XE).
Cisco Software Checker
Official documentation
Official tool to confirm whether your exact IOS / IOS XE / NX-OS / ASA / FTD / SD-WAN release is affected and to find the first fixed release.

Discussion(0)

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