What is CVE-2020-9444?

CVE-2020-9444 is a medium-severity vulnerability in Zulip Server, classified under Improper Restriction of Rendered UI Layers or Frames (Clickjacking). CVSS score: 6.1/10. Published 2020-04-20.

How severe is CVE-2020-9444?

Medium severity. CVSS v3 base score is 6.1 out of 10.

Vulnerability in Zulip Server

CVE-2020-9444

Zulip Server before 2.1.3 allows reverse tabnabbing via the Markdown functionality.

Published 2020-04-20 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 6.1 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N.

EPSS exploit prediction

EPSS: 0.007 (51.4th percentile), scored 2026-10-23.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 51st percentile — 51.4% 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

Zulip Server

Weakness classification (CWE)

CWE-1021 — Improper Restriction of Rendered UI Layers or Frames (Clickjacking)

References

blog.zulip.org/2020/04/01/zulip-server-2-1-3-security-release/ (Vendor Advisory)

Frequently asked questions

What is CVE-2020-9444?: CVE-2020-9444 is a medium-severity vulnerability in Zulip Server, classified under Improper Restriction of Rendered UI Layers or Frames (Clickjacking). CVSS score: 6.1/10. Published 2020-04-20.
How severe is CVE-2020-9444?: Medium severity. CVSS v3 base score is 6.1 out of 10.