CVE-2026-6673

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

State: Published
Severity: 6.4 Medium
Published: Jun 22, 2026
Updated: Jun 22, 2026
Reserved: Apr 20, 2026

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

Scores

CVSS	Score	Vector	Source
3.1	6.4 Medium	CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:N/I:H/A:H	Mattermost

Weaknesses

CWE-306 Missing Authentication for Critical Function

Affected Products

Product	Versions
MattermostMattermost	11.7.0 through 11.7.0Affected 11.6.0 through 11.6.2Affected 11.5.0 through 11.5.5Affected 10.11.0 through 10.11.17Affected 11.8.0Not affected 11.7.1Not affected 11.6.3Not affected 11.5.6Not affected 10.11.18Not affected

References

MMSA-2026-00654vendor-advisory

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