What is CVE-2018-3761?

CVE-2018-3761 is a high-severity vulnerability in Nextcloud Server, classified under Improper Authentication. CVSS score: 8.1/10. Published 2018-07-05.

How severe is CVE-2018-3761?

High severity. CVSS v3 base score is 8.1 out of 10.

Auth bypass in Nextcloud Server

CVE-2018-3761

Nextcloud Server before 12.0.8 and 13.0.3 suffer from improper authentication on the OAuth2 token endpoint. Missing checks potentially allowed handing out new tokens in case the OAuth2 client was partly compromised.

Vulnerability class: Broken Authentication

Published 2018-07-05 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 8.1 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N.

EPSS exploit prediction

EPSS: 0.017 (75.7th percentile), scored 2026-09-29.

Low probability of exploitation in the next 30 days, but still tracked. 76th percentile — 75.7% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.017 · newest: 0.017 · change: 0.000

Affected products

Nextcloud Server — versions <13.0.3, <12.0.8
Nextcloud Server

Weakness classification (CWE)

CWE-287 — Improper Authentication

References

hackerone.com/reports/343111 (Third Party Advisory)
nextcloud.com/security/advisory/ (Broken Link, Vendor Advisory)

Frequently asked questions

What is CVE-2018-3761?: CVE-2018-3761 is a high-severity vulnerability in Nextcloud Server, classified under Improper Authentication. CVSS score: 8.1/10. Published 2018-07-05.
How severe is CVE-2018-3761?: High severity. CVSS v3 base score is 8.1 out of 10.