What is CVE-2021-21439?

CVE-2021-21439 is a medium-severity vulnerability in Otrs, classified under Improper Check for Unusual or Exceptional Conditions. CVSS score: 6.5/10. Published 2021-06-14.

How severe is CVE-2021-21439?

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

Vulnerability in Otrs

CVE-2021-21439

DoS attack can be performed when an email contains specially designed URL in the body. It can lead to the high CPU usage and cause low quality of service, or in extreme case bring the system to a halt. This issue affects: OTRS AG ((OTRS)) Community Edition 6.0.x version 6.0.1 and later versions. OTRS AG OTRS 7.0.x version 7.0.26 and prior versions; 8.0.x version 8.0.13 and prior versions.

Published 2021-06-14 · 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: 0.009 (57.4th percentile), scored 2026-09-29.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 57th percentile — 57.4% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.010 · newest: 0.009 · change: -0.001

Affected products

Otrs
Otrs Ag — versions 7.0.x, 8.0.x
Otrs Ag ((Otrs)) Community Edition — versions 6.0.1

Weakness classification (CWE)

References

otrs.com/release-notes/otrs-security-advisory-2021-09/ (Vendor Advisory)
lists.debian.org/debian-lts-announce/2023/08/msg00040.html (mailing-list)

Frequently asked questions

What is CVE-2021-21439?: CVE-2021-21439 is a medium-severity vulnerability in Otrs, classified under Improper Check for Unusual or Exceptional Conditions. CVSS score: 6.5/10. Published 2021-06-14.
How severe is CVE-2021-21439?: Medium severity. CVSS v3 base score is 6.5 out of 10.