CVE-2021-1453

What it is

A vulnerability in the software image verification functionality of Cisco IOS XE Software for the Cisco Catalyst 9000 Family of switches could allow an unauthenticated, physical attacker to execute unsigned code at system boot time. The vulnerability is due to an improper check in the code function that manages the verification of the digital signatures of system image files during the initial boot process. An attacker could exploit this vulnerability by loading unsigned software on an affected device. A successful exploit could allow the attacker to boot a malicious software image or execute unsigned code and bypass the image verification check part of the secure boot process of an affected device. To exploit this vulnerability, the attacker would need to have unauthenticated physical access to the device or obtain privileged access to the root shell on the device.

At a glance

Exploitability

Can be exploited with physical access without logging in. High risk of data exposure, data tampering, service disruption.

Exploit odds

0.2% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2021-03-24 20:15 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-06-17 03:31 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 0.2% in the next 30 days (EPSS).
• Severity: 6.8 MEDIUM (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2021-03-24 20:15 UTC

Last modified

2026-06-17 03:31 UTC

Exploit probability

0.2% · EPSS, next 30 days

Weakness

CWE-347

Record status

Modified

Affected

• Cisco iOS Xe 3.15.1xbs
• Cisco iOS Xe 3.15.2xbs
• Cisco iOS Xe 16.6.1
• Cisco iOS Xe 16.6.2
• Cisco iOS Xe 16.6.3
• Cisco iOS Xe 16.6.4
• Cisco iOS Xe 16.6.4a
• Cisco iOS Xe 16.6.4s

Attack profile CVSS 3.1 · 6.8

Attack vector

Physical

Complexity

Low

Privileges needed

None

User interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2021-1453.md and follow it. Check whether this project is affected by CVE-2021-1453. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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