CVE-2021-1376

What it is

Multiple vulnerabilities in the fast reload feature of Cisco IOS XE Software running on Cisco Catalyst 3850, Cisco Catalyst 9300, and Cisco Catalyst 9300L Series Switches could allow an authenticated, local attacker to either execute arbitrary code on the underlying operating system, install and boot a malicious software image, or execute unsigned binaries on an affected device. These vulnerabilities are due to improper checks performed by system boot routines. To exploit these vulnerabilities, the attacker would need privileged access to the CLI of the device. A successful exploit could allow the attacker to either execute arbitrary code on the underlying operating system or execute unsigned code and bypass the image verification check part of the secure boot process. For more information about these vulnerabilities, see the Details section of this advisory.

At a glance

Exploitability

Can be exploited locally on the machine with an admin-level account. 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 21:15 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: 6.7 MEDIUM (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2021-03-24 21:15 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 16.5.1
• Cisco iOS Xe 16.5.1a
• 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 · 6.7

Attack vector

Local

Complexity

Low

Privileges needed

High

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-2021-1376.md and follow it. Check whether this project is affected by CVE-2021-1376. 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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