What is CVE-2021-39220?

CVE-2021-39220 is a low-severity vulnerability in Nextcloud Mail, classified under Improper Input Validation. CVSS score: 3.5/10. Published 2021-10-25.

How severe is CVE-2021-39220?

Low severity. CVSS v3 base score is 3.5 out of 10.

Information disclosure in Nextcloud Mail

CVE-2021-39220

Nextcloud is an open-source, self-hosted productivity platform The Nextcloud Mail application prior to versions 1.10.4 and 1.11.0 does by default not render images in emails to not leak the read state or user IP. The privacy filter failed to filter images with a relative protocol. It is recommended that the Nextcloud Mail application is upgraded to 1.10.4 or 1.11.0. There are no known workarounds aside from upgrading.

Vulnerability class: Drupalgeddon 2 (CVE-2018-7600)

Published 2021-10-25 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 3.5 (Low). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:N/A:N.

EPSS exploit prediction

EPSS: 0.008 (54.3th percentile), scored 2026-09-30.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 54th percentile — 54.3% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.008 · newest: 0.008 · change: 0.000

Affected products

Nextcloud Mail
Nextcloud Security-Advisories — versions < 1.10.4, < 1.11.0

Weakness classification (CWE)

References

github.com/nextcloud/security-advisories/security/advisories/GHSA-6q9v-wm8r-rcv5 (Third Party Advisory)
github.com/nextcloud/mail/pull/5470 (Patch, Third Party Advisory)
hackerone.com/reports/1308147 (Permissions Required)

Frequently asked questions

What is CVE-2021-39220?: CVE-2021-39220 is a low-severity vulnerability in Nextcloud Mail, classified under Improper Input Validation. CVSS score: 3.5/10. Published 2021-10-25.
How severe is CVE-2021-39220?: Low severity. CVSS v3 base score is 3.5 out of 10.