What is CVE-2021-1399?

CVE-2021-1399 is a medium-severity vulnerability in Cisco Unified Communications Manager, classified under Authentication Bypass by Assumed-Immutable Data. CVSS score: 4.3/10. Published 2021-04-08.

How severe is CVE-2021-1399?

Medium severity. CVSS v3 base score is 4.3 out of 10.

Vulnerability in Cisco Unified Communications Manager

CVE-2021-1399

A vulnerability in the Self Care Portal of Cisco Unified Communications Manager (Unified CM) and Cisco Unified Communications Manager Session Management Edition (Unified CM SME) could allow an authenticated, remote attacker to modify data on an affected system without proper authorization. The vulnerability is due to insufficient validation of user-supplied data to the Self Care Portal. An attacker could exploit this vulnerability by sending a crafted HTTP request to an affected system. A successful exploit could allow the attacker to modify information without proper authorization.

Published 2021-04-08 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 4.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N.

EPSS exploit prediction

EPSS: 0.006 (48.4th percentile), scored 2026-10-18.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 48th percentile — 48.4% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.006 · newest: 0.006 · change: 0.000

Affected products

Weakness classification (CWE)

CWE-302 — Authentication Bypass by Assumed-Immutable Data

References

tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-cucm-sel… (vendor-advisory, Vendor Advisory)

Frequently asked questions

What is CVE-2021-1399?: CVE-2021-1399 is a medium-severity vulnerability in Cisco Unified Communications Manager, classified under Authentication Bypass by Assumed-Immutable Data. CVSS score: 4.3/10. Published 2021-04-08.
How severe is CVE-2021-1399?: Medium severity. CVSS v3 base score is 4.3 out of 10.