What is CVE-2023-25820?

CVE-2023-25820 is a medium-severity vulnerability in Nextcloud Server, classified under Improper Restriction of Excessive Authentication Attempts. CVSS score: 4.2/10. Published 2023-03-22.

How severe is CVE-2023-25820?

Medium severity. CVSS v3 base score is 4.2 out of 10.

Vulnerability in Nextcloud Server

CVE-2023-25820

Nextcloud Server is the file server software for Nextcloud, a self-hosted productivity platform, and Nextcloud Enterprise Server is the enterprise version of the file server software. In Nextcloud Server versions 25.0.x prior to 25.0.5 and versions 24.0.x prior to 24.0.10 as well as Nextcloud Enterprise Server versions 25.0.x prior to 25.0.4, 24.0.x prior to 24.0.10, 23.0.x prior to 23.0.12.5, 22.x prior to 22.2.0.10, and 21.x prior to 21.0.9.10, when an attacker gets access to an already logged in user session they can then brute force the password on the confirmation endpoint. Nextcloud Server should upgraded to 24.0.10 or 25.0.4 and Nextcloud Enterprise Server should upgraded to 21.0.9.10, 22.2.10.10, 23.0.12.5, 24.0.10, or 25.0.4 to receive a patch. No known workarounds are available.

Published 2023-03-22 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 4.2 (Medium). Vector: CVSS:3.1/AV:L/AC:H/PR:L/UI:R/S:U/C:L/I:L/A:L.

EPSS exploit prediction

EPSS: 0.002 (13.0th percentile), scored 2026-09-29.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 13th percentile — 13.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.002 · newest: 0.002 · change: 0.000

Affected products

Nextcloud Server
Nextcloud Security-Advisories — versions Nextcloud Server >= 24.0.0, < 24.0.10, Nextcloud Server >= 25.0.0, < 25.0.4, Nextcloud Enterprise Server >= 25.0.0, < 25.0.4

Weakness classification (CWE)

CWE-307 — Improper Restriction of Excessive Authentication Attempts

References

github.com/nextcloud/security-advisories/security/advisories/GHSA-36g6-wjx2-333x (Vendor Advisory)
github.com/nextcloud/server/pull/36489 (Patch)
hackerone.com/reports/1842114 (Third Party Advisory)

Frequently asked questions

What is CVE-2023-25820?: CVE-2023-25820 is a medium-severity vulnerability in Nextcloud Server, classified under Improper Restriction of Excessive Authentication Attempts. CVSS score: 4.2/10. Published 2023-03-22.
How severe is CVE-2023-25820?: Medium severity. CVSS v3 base score is 4.2 out of 10.