🛡️ CVE-2026-6673 — mattermost-server

🟡 CVSS 6.4 — Medium ✅ No Known Exploit CWE-306 NVD
6.4
CVSS Score
0 Low4 Medium7 High9 Critical10

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

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is high, an attacker needs low-level privileges on the target. A user must be tricked into taking some action. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality none, integrity high, availability high.

Weakness class

CVE-2026-6673 is classified as CWE-306: Missing Authentication for Critical Function. A sensitive function can be reached without authenticating at all.

Affected software

CVE-2026-6673 is recorded against 1 package.

  • mattermost-server (from 11.7.0 up to 11.7.1)

Timeline and source

Published on 22 June 2026 and last revised on 23 June 2026. No public exploit is currently recorded for this entry. Record sourced from NVD.

References

mattermost.com

Details

Severity MEDIUM
CVSS Score 6.4
CVSS Vector CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:N/I:H/A:H
CWE CWE-306
Public Exploit ✅ No
Source NVD
Published 2026-06-22
Updated 2026-08-11
Modified 2026-06-23
Fix URL N/A

Affected Packages

Software From version Fixed in
mattermost-server 11.7.0 11.7.1

References

Similar Threats

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