CVE-2021-1136

What it is

Multiple vulnerabilities in Cisco Network Convergence System (NCS) 540 Series Routers, only when running Cisco IOS XR NCS540L software images, and Cisco IOS XR Software for the Cisco 8000 Series Routers could allow an authenticated, local attacker to execute unsigned code during the boot process on an affected device. 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. 2021-02-04 17:15 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

2021-02-04 17:15 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 Xr < 7.0.12
• Cisco iOS Xr < 7.2.1

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-2021-1136.md and follow it. Check whether this project is affected by CVE-2021-1136. 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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