What is CVE-2021-22896?

CVE-2021-22896 is a medium-severity vulnerability in Nextcloud, classified under Missing Authorization. CVSS score: 4.3/10. Published 2021-06-11.

How severe is CVE-2021-22896?

Medium severity. CVSS v3 base score is 4.3 out of 10.

Auth bypass in Nextcloud

CVE-2021-22896

Nextcloud Mail before 1.9.5 suffers from improper access control due to a missing permission check allowing other authenticated users to create mail aliases for other users.

Vulnerability class: Broken Access Control

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

CVSS v3 metric

CVSS v3 base score 4.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N.

EPSS exploit prediction

EPSS: 0.010 (61.0th percentile), scored 2026-09-29.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 61st percentile — 61.0% 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: 0.010 · change: 0.000

Affected products

Nextcloud
Nextcloud Mail — versions Fixed in 1.9.5

Weakness classification (CWE)

CWE-862 — Missing Authorization

References

hackerone.com/reports/1129996 (Third Party Advisory)
github.com/nextcloud/security-advisories/security/advisories/GHSA-jmgp-77jq-fjp3 (Third Party Advisory)
github.com/nextcloud/mail/pull/4864 (Patch, Third Party Advisory)
github.com/nextcloud/mail/releases/tag/v1.9.5 (Third Party Advisory, Release Notes)

Frequently asked questions

What is CVE-2021-22896?: CVE-2021-22896 is a medium-severity vulnerability in Nextcloud, classified under Missing Authorization. CVSS score: 4.3/10. Published 2021-06-11.
How severe is CVE-2021-22896?: Medium severity. CVSS v3 base score is 4.3 out of 10.