What is CVE-2016-6421?

CVE-2016-6421 is a medium-severity vulnerability in Cisco iOS Xr, classified under CWE-399. CVSS score: 5.3/10. Published 2016-10-05.

How severe is CVE-2016-6421?

Medium severity. CVSS v3 base score is 5.3 out of 10.

Vulnerability in Cisco iOS Xr

CVE-2016-6421

Cisco IOS XR 5.2.2 allows remote attackers to cause a denial of service (process restart) via a crafted OSPF Link State Advertisement (LSA) update, aka Bug ID CSCvb05643.

Published 2016-10-05 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 5.3 (Medium). Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L.

EPSS exploit prediction

EPSS: 0.016 (74.9th percentile), scored 2026-10-02.

Low probability of exploitation in the next 30 days, but still tracked. 75th percentile — 74.9% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.016 · newest: 0.016 · change: 0.000

Affected products

Cisco iOS Xr — versions 5.2.2

Weakness classification (CWE)

CWE-399

References

tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20160928… (vendor-advisory, Vendor Advisory)
www.securityfocus.com/bid/93212 (vdb-entry)
www.securitytracker.com/id/1036909 (vdb-entry)

Frequently asked questions

What is CVE-2016-6421?: CVE-2016-6421 is a medium-severity vulnerability in Cisco iOS Xr, classified under CWE-399. CVSS score: 5.3/10. Published 2016-10-05.
How severe is CVE-2016-6421?: Medium severity. CVSS v3 base score is 5.3 out of 10.