What is CVE-2020-8139?

CVE-2020-8139 is a medium-severity vulnerability in Nextcloud Server, classified under Improper Access Control. CVSS score: 6.5/10. Published 2020-03-20.

How severe is CVE-2020-8139?

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

Auth bypass in Nextcloud Server

CVE-2020-8139

A missing access control check in Nextcloud Server < 18.0.1, < 17.0.4, and < 16.0.9 causes hide-download shares to be downloadable when appending /download to the URL.

Published 2020-03-20 · 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:H/I:N/A:N.

EPSS exploit prediction

EPSS: 0.015 (73.8th percentile), scored 2026-09-29.

Low probability of exploitation in the next 30 days, but still tracked. 74th percentile — 73.8% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.015 · newest: 0.015 · change: 0.000

Affected products

Nextcloud Server
Fedoraproject Fedora — versions 32
Nextcloud Server — versions Fixed in 18.0.1, 17.0.4, and 16.0.9

Weakness classification (CWE)

References

hackerone.com/reports/788257 (Permissions Required)
nextcloud.com/security/advisory/ (Vendor Advisory)
lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/… (vendor-advisory)

Frequently asked questions

What is CVE-2020-8139?: CVE-2020-8139 is a medium-severity vulnerability in Nextcloud Server, classified under Improper Access Control. CVSS score: 6.5/10. Published 2020-03-20.
How severe is CVE-2020-8139?: Medium severity. CVSS v3 base score is 6.5 out of 10.