CVE-2026-6673

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

CVSS 6.4 MEDIUMEPSS 0.2%CWE-306

Vexday Risk Score

13Low

SSVC decision (CISA)

Track

No exploitation signal → monitor

CVSS 6.4EPSS 0.2%KEV nãoPoC —Nuclei —Metasploit —Patch referenciado

Lifecycle

22 Jun 2026Published on NVD

Recommendation: Monitor — no exploitation signal at the moment.

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

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

Affected products

Mattermost · Mattermost

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References

https://mattermost.com/security-updates