CVE-2026-0999

Name: CVE-2026-0999
Creator: NVD / NIST
Published: 2026-02-16T10:16:08.14+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

MEDIUMCVSS 4.3/10EPSS 0.17%

Last modified Jun 17, 2026

CVE-2026-0999 is a medium-severity vulnerability rated 4.3/10 on the CVSS scale. Mattermost versions 11.1.x <= 11.1.2, 10.11.x <= 10.11.9, 11.2.x <= 11.2.1 fail to properly validate login method restrictions which allows an authenticated user to bypass SSO-only login requirements via userID-based authentication. Mattermost Advisory ID: MMSA-2025-00548. EPSS estimates a 0.17% chance of exploitation in the next 30 days.

Description

Mattermost versions 11.1.x <= 11.1.2, 10.11.x <= 10.11.9, 11.2.x <= 11.2.1 fail to properly validate login method restrictions which allows an authenticated user to bypass SSO-only login requirements via userID-based authentication. Mattermost Advisory ID: MMSA-2025-00548

Metrics

CVSS 3.1

4.3/10

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N

EPSS Probability

0.17%

6.9th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-303

Affected Software

Vendor	Product	Versions
Mattermost	Mattermost Server	>= 10.11.0, < 10.11.10
Mattermost	Mattermost Server	>= 11.1.0, < 11.1.3
Mattermost	Mattermost Server	>= 11.2.0, < 11.2.2

References

https://mattermost.com/security-updatesVendor Advisory

Timeline

Published: Feb 16, 2026
Last Modified: Jun 17, 2026
Status: Analyzed

Frequently Asked Questions

What is CVE-2026-0999?

How severe is CVE-2026-0999?

CVE-2026-0999 has a CVSS score of 4.3/10 (MEDIUM severity). The EPSS model estimates a 0.17% probability of exploitation in the next 30 days.

How do I fix CVE-2026-0999?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2026-0999?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST