What is CVE-2021-20634?

CVE-2021-20634 is a medium-severity vulnerability in Cybozu Office. CVSS score: 4.3/10. Published 2021-03-18.

How severe is CVE-2021-20634?

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

Vulnerability in Cybozu Office

CVE-2021-20634

Improper access control vulnerability in Custom App of Cybozu Office 10.0.0 to 10.8.4 allows authenticated attackers to bypass access restriction and obtain the date of Custom App via unspecified vectors.

Published 2021-03-18 · 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:L/I:N/A:N.

EPSS exploit prediction

EPSS: 0.007 (52.1th percentile), scored 2026-09-30.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 52nd percentile — 52.1% 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 Office
Cybozu, Inc. Cybozu Office — versions 10.0.0 to 10.8.4

References

jvn.jp/en/jp/JVN45797538/index.html (Third Party Advisory)
kb.cybozu.support/article/36865/ (Vendor Advisory)

Frequently asked questions

What is CVE-2021-20634?: CVE-2021-20634 is a medium-severity vulnerability in Cybozu Office. CVSS score: 4.3/10. Published 2021-03-18.
How severe is CVE-2021-20634?: Medium severity. CVSS v3 base score is 4.3 out of 10.