CVE-2026-6673

MEDIUM

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

Title source: cna
STIX 2.1

Description

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

References (1)

Core 1
Core References
Vendor Advisory vendor-advisory
MMSA-2026-00654
https://mattermost.com/security-updates

Scores

CVSS v3 6.4
EPSS 0.0018
EPSS Percentile 7.4%
Attack Vector NETWORK
CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:N/I:H/A:H

CISA SSVC

Vulnrichment
Exploitation none
Automatable no
Technical Impact partial

Details

CWE
CWE-306
Status published
Products (10)
Mattermost/Mattermost 10.11.0 - 10.11.17
Mattermost/Mattermost 10.11.18
Mattermost/Mattermost 11.5.0 - 11.5.5
Mattermost/Mattermost 11.5.6
Mattermost/Mattermost 11.6.0 - 11.6.2
Mattermost/Mattermost 11.6.3
Mattermost/Mattermost 11.7.0
Mattermost/Mattermost 11.7.1
Mattermost/Mattermost 11.8.0
mattermost/mattermost_server 10.11.0 - 10.11.18
Published Jun 22, 2026
Tracked Since Jun 22, 2026