What is CVE-2021-1136?

CVE-2021-1136 is a medium-severity vulnerability in Cisco 8201, classified under Improper Verification of Cryptographic Signature. CVSS score: 6.7/10. Published 2021-02-04.

How severe is CVE-2021-1136?

Medium severity. CVSS v3 base score is 6.7 out of 10.

Vulnerability in Cisco 8201

CVE-2021-1136

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.

Published 2021-02-04 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 6.7 (Medium). Vector: CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.002 (9.3th percentile), scored 2026-09-29.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 9th percentile — 9.3% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.002 · newest: 0.002 · change: 0.000

Affected products

Weakness classification (CWE)

CWE-347 — Improper Verification of Cryptographic Signature

References

tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ioxr-l-z… (vendor-advisory, Vendor Advisory)

Frequently asked questions

What is CVE-2021-1136?: CVE-2021-1136 is a medium-severity vulnerability in Cisco 8201, classified under Improper Verification of Cryptographic Signature. CVSS score: 6.7/10. Published 2021-02-04.
How severe is CVE-2021-1136?: Medium severity. CVSS v3 base score is 6.7 out of 10.