CVE-2026-20104
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.
Key facts
- CVSS score
- 6.1 (v3.1)
- Severity
- MEDIUM
- CVSS vector
CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N- Weakness (CWE)
- CWE-124
- EPSS score
- 0.2% (4th percentile)
- In CISA KEV
- No
- In EU EUVD
- Yes (EUVD-2026-15435)
- Published
- March 25, 2026
- NVD last modified
- September 28, 2026
- Status
- Analyzed
EU Vulnerability Database (EUVD)
This vulnerability is also tracked by ENISA as EUVD-2026-15435 in the EU Vulnerability Database. Last updated in EUVD on March 26, 2026.
View on the EU Vulnerability DatabaseAffected products
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Certified products that may be affected
11 FIPS 140 or Common Criteria certified products, from automated matching by sec-certs.org.
- Cisco Embedded Services 9300 and 3300 Series Switches (ESS9300 & ESS3300) running IOS-XE 17.15 - Cisco Systems, Inc. - Common Criteria CCEVS-VR-VID-11662-2026 - active
- Cisco Catalyst 8000V Edge (C8000V) running IOS-XE 17.15 - Cisco Systems, Inc. - Common Criteria Certificate Number: 2025/161 - active
- Cisco 1000 Series Integrated Services Routers (C1100), Cisco Catalyst IR1800 Rugged Series Routers (IR1800), Cisco Catalyst IR8300 Rugged Series Routers (IR8300) running IOS-XE 17.15 - Cisco Systems, Inc. - Common Criteria CCEVS-VR-VID-11643-2025 - active
- Cisco Catalyst Industrial Ethernet 9300 Rugged Series Switches running IOS-XE 17.15 - Cisco Systems, Inc. - Common Criteria CCEVS-VR-VID-11603-2025 - active
- Cisco Aggregation Services Router 1000 Series (ASR1K), Cisco Catalyst 8200, 8300, 8500 Series Edge Routers (Cat8K) running IOS-XE version 17.15 - Cisco Systems, Inc. - Common Criteria CCEVS-VR-VID-11642-2025 - active
See all 11 in the Security Certifications Explorer.
References
Last updated September 30, 2026 · Source: NVD, CISA KEV, FIRST.org EPSS
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