What is CVE-2026-6673?

CVE-2026-6673 is a medium-severity vulnerability in Mattermost, classified under Missing Authentication for Critical Function. CVSS score: 6.4/10. Published 2026-06-22.

How severe is CVE-2026-6673?

Medium severity. CVSS v3 base score is 6.4 out of 10.

Auth bypass in Mattermost

CVE-2026-6673

Mattermost versions 11.7.x <= 11.7.0, 11.6.x <= 11.6.2, 11.5.x <= 11.5.5, 10.11.x <= 10.11.17 fail to authenticate Atlassian Connect installed callbacks, allowing a remote unauthenticated attacker to inject a rogue sharedSecret and disrupt…

Vulnerability class: Broken Authentication

CVSS v3 metric

CVSS v3 base score 6.4 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:N/I:H/A:H.

Affected products

Mattermost — versions 11.7.0, 11.6.0, 11.5.0

Weakness classification (CWE)

CWE-306 — Missing Authentication for Critical Function

References

responsibledisclosure@mattermost.com (vendor-advisory)

Frequently asked questions

What is CVE-2026-6673?: CVE-2026-6673 is a medium-severity vulnerability in Mattermost, classified under Missing Authentication for Critical Function. CVSS score: 6.4/10. Published 2026-06-22.
How severe is CVE-2026-6673?: Medium severity. CVSS v3 base score is 6.4 out of 10.