What is CVE-2021-20803?

CVE-2021-20803 is a medium-severity vulnerability in Cybozu Remote Service Manager, classified under Incorrect Authorization. CVSS score: 5.4/10. Published 2021-10-13.

How severe is CVE-2021-20803?

Medium severity. CVSS v3 base score is 5.4 out of 10.

Auth bypass in Cybozu Remote Service Manager

CVE-2021-20803

Operation restriction bypass in the management screen of Cybozu Remote Service 3.1.8 to 3.1.9 allows a remote authenticated attacker to alter the data of the management screen.

Vulnerability class: Broken Access Control

Published 2021-10-13 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 5.4 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L.

EPSS exploit prediction

EPSS: 0.007 (51.9th percentile), scored 2026-09-30.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 52nd percentile — 51.9% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.007 · newest: 0.007 · change: 0.000

Affected products

Cybozu Remote Service Manager — versions 3.1.8, 3.1.9
Cybozu, Inc. Cybozu Remote Service — versions 3.1.8 to 3.1.9

Weakness classification (CWE)

CWE-863 — Incorrect Authorization

References

jvn.jp/en/jp/JVN52694228/index.html (Third Party Advisory)
kb.cybozu.support/article/37421 (Vendor Advisory)

Frequently asked questions

What is CVE-2021-20803?: CVE-2021-20803 is a medium-severity vulnerability in Cybozu Remote Service Manager, classified under Incorrect Authorization. CVSS score: 5.4/10. Published 2021-10-13.
How severe is CVE-2021-20803?: Medium severity. CVSS v3 base score is 5.4 out of 10.