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CVE-2026-6673— Mattermost Jira plugin had unauthenticated {{/ac/installed}} lifecycle callback during pending Jira Cloud install

Quick assessment

Affected
Mattermost Mattermost
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Mattermost是美国Mattermost公司开源的一个开源协作平台。 Mattermost存在授权问题漏洞，该漏洞源于未对Atlassian Connect安装的回调进行身份验证，可能导致远程未认证的攻击者注入恶意sharedSecret并通过向/ac/installed发起POST请求破坏Jira集成。以下版本受到影响：11.7.0及之前的11.7.x版本、11.6.2及之前的11.6.x版本、11.5.5及之前的11.5.x版本和10.11.17及之前的10.11.x版本。

CVSS 6.4 · Medium EPSS 0.30% · P21

Affected Version Matrix 9

VendorProduct Version RangeStatus
Mattermost Mattermost 11.7.0≤ 11.7.0 affected
11.6.0≤ 11.6.2 affected
11.5.0≤ 11.5.5 affected
10.11.0≤ 10.11.17 affected
11.8.0 unaffected
11.7.1 unaffected
11.6.3 unaffected
11.5.6 unaffected
… +1 more rows
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I. Basic Information for CVE-2026-6673

Vulnerability Information
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Although we use advanced large model technology, its output may still contain inaccurate or outdated information.Shenlong tries to ensure data accuracy, but please verify and judge based on the actual situation.

Vulnerability Title
Mattermost Jira plugin had unauthenticated {{/ac/installed}} lifecycle callback during pending Jira Cloud install
Source: CVE Program / CVE List V5
Vulnerability 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
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:N/I:H/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
关键功能的认证机制缺失
Source: CVE Program / CVE List V5
Vulnerability Title
Mattermost 授权问题漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Mattermost是美国Mattermost公司开源的一个开源协作平台。 Mattermost存在授权问题漏洞，该漏洞源于未对Atlassian Connect安装的回调进行身份验证，可能导致远程未认证的攻击者注入恶意sharedSecret并通过向/ac/installed发起POST请求破坏Jira集成。以下版本受到影响：11.7.0及之前的11.7.x版本、11.6.2及之前的11.6.x版本、11.5.5及之前的11.5.x版本和10.11.17及之前的10.11.x版本。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Mattermost Mattermost 11.7.0 ~ 11.7.0 -

II. Public POCs for CVE-2026-6673

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III. Intelligence Information for CVE-2026-6673

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Same Patch Batch · Mattermost · 2026-06-22 · 6 CVEs total

CVE-2026-6062 6.4 MEDIUM IDOR in Jira plugin subscription edit endpoint
CVE-2026-5139 5.4 MEDIUM GitLab Plugin Allows Non-Admin Users to Modify Default Instance Configuration
CVE-2026-9162 4.3 MEDIUM Global session revocation does not invalidate active WebSocket connections
CVE-2026-8823 3.8 LOW User Manager can demote bot accounts to guest without bot-management permission
CVE-2026-8074 3.8 LOW Improper Permission Check Allows User Manager to Deactivate Bot Accounts

IV. Related Vulnerabilities

Same product: Mattermost
Same vendor: Mattermost
Same weakness: CWE-306

V. Comments for CVE-2026-6673

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