CVE-2021-1390

What it is

A vulnerability in one of the diagnostic test CLI commands of Cisco IOS XE Software could allow an authenticated, local attacker to execute arbitrary code on an affected device. To exploit this vulnerability, the attacker would need to have valid user credentials at privilege level 15. This vulnerability exists because the affected software permits modification of the run-time memory of an affected device under specific circumstances. An attacker could exploit this vulnerability by authenticating to the affected device and issuing a specific diagnostic test command at the CLI. A successful exploit could trigger a logic error in the code that was designed to restrict run-time memory modifications. The attacker could take advantage of this logic error to overwrite system memory locations and execute arbitrary code on the underlying Linux operating system (OS) of the affected device.

At a glance

Exploitability

Can be exploited locally on the machine with an admin-level account. High risk of data tampering.

Exploit odds

0.3% 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: 0.3% in the next 30 days (EPSS).
• Severity: 5.1 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

0.3% · EPSS, next 30 days

Weakness

CWE-123

Record status

Modified

Affected

• Cisco iOS Xe 16.8.1
• Cisco iOS Xe 16.8.1a
• Cisco iOS Xe 16.8.1b
• Cisco iOS Xe 16.8.1c
• Cisco iOS Xe 16.8.1d
• Cisco iOS Xe 16.8.1e
• Cisco iOS Xe 16.8.1s
• Cisco iOS Xe 16.8.2

Attack profile CVSS 3.1 · 5.1

Attack vector

Local

Complexity

Low

Privileges needed

High

User interaction

None

Scope

Unchanged

Confidentiality

Low

Integrity

High

Availability

None

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-2021-1390.md and follow it. Check whether this project is affected by CVE-2021-1390. 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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