CVE-2026-6673CWE-306

Mattermost Jira plugin had unauthenticated {{/ac/installed}} lifecycle callback during pending Jira Cloud install

Medium · published June 22, 2026

CVSS v3.1
6.4
EPSS
0%
Percentile
21.4
In the wild
Unconfirmed
What it is

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 the Jira integration via POST to /ac/installed during the pending-install window.. Mattermost Advisory ID: MMSA-2026-00654

The record
Technical detail
CVSS v3.1
6.4 · MEDIUM
Vector
CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:N/I:H/A:H
CVSS v4.0
Not supplied
EPSS
0.00299 · 21.4th percentile
Weakness
CWE-306 · Missing Authentication for Critical Function
Published
2026-06-22T13:38Z
EPSS history
Timeline
  • 22 JUN 13:38Z
    Mattermost Jira plugin had unauthenticated {{/ac/installed}} lifecycle callback during pending Jira Cloud install
    cvelistv5