What is CVE-2021-20839?

CVE-2021-20839 is a medium-severity vulnerability in Antennahouse Office Server Document Converter, classified under Improper Restriction of XML External Entity Reference (XXE). CVSS score: 6.5/10. Published 2021-11-01.

How severe is CVE-2021-20839?

Medium severity. CVSS v3 base score is 6.5 out of 10.

XXE in Antennahouse Office Server Document Converter

CVE-2021-20839

Office Server Document Converter V7.2MR4 and earlier and V7.1MR7 and earlier allows a remote unauthenticated attacker to conduct an XML External Entity (XXE) attack to cause a denial of service (DoS) condition to the other servers by processing a specially crafted XML document.

Vulnerability class: XXE (XML External Entity)

Published 2021-11-01 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 6.5 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H.

EPSS exploit prediction

EPSS: 0.011 (65.4th percentile), scored 2026-10-03.

Low probability of exploitation in the next 30 days, but still tracked. 65th percentile — 65.4% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.011 · newest: 0.011 · change: 0.000

Affected products

Antennahouse Office Server Document Converter — versions 5.2, 6.0, 6.1
Antenna House, Inc. Office Server Document Converter — versions V7.2MR4 and earlier and V7.1MR7 and earlier

Weakness classification (CWE)

CWE-611 — Improper Restriction of XML External Entity Reference (XXE)

References

www.antenna.co.jp/news/2021/osdc72-20211027.html (Patch, Vendor Advisory)
jvn.jp/en/jp/JVN33453839/index.html (Third Party Advisory)

Frequently asked questions

What is CVE-2021-20839?: CVE-2021-20839 is a medium-severity vulnerability in Antennahouse Office Server Document Converter, classified under Improper Restriction of XML External Entity Reference (XXE). CVSS score: 6.5/10. Published 2021-11-01.
How severe is CVE-2021-20839?: Medium severity. CVSS v3 base score is 6.5 out of 10.