What is CVE-2021-42084?

CVE-2021-42084 is a medium-severity vulnerability in Zammad, classified under Loop with Unreachable Exit Condition (Infinite Loop). CVSS score: 6.5/10. Published 2021-10-07.

How severe is CVE-2021-42084?

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

Vulnerability in Zammad

CVE-2021-42084

An issue was discovered in Zammad before 4.1.1. An attacker with valid agent credentials may send a series of crafted requests that cause an endless loop and thus cause denial of service.

Published 2021-10-07 · last modified 2026-06-17.

CVSS v3 metric

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

EPSS exploit prediction

EPSS: 0.009 (59.0th percentile), scored 2026-09-30.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 59th percentile — 59.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.009 · newest: 0.009 · change: 0.000

Affected products

Zammad

Weakness classification (CWE)

CWE-835 — Loop with Unreachable Exit Condition (Infinite Loop)

References

zammad.com/en/advisories/zaa-2021-11 (Vendor Advisory)

Frequently asked questions

What is CVE-2021-42084?: CVE-2021-42084 is a medium-severity vulnerability in Zammad, classified under Loop with Unreachable Exit Condition (Infinite Loop). CVSS score: 6.5/10. Published 2021-10-07.
How severe is CVE-2021-42084?: Medium severity. CVSS v3 base score is 6.5 out of 10.