CVE-2026-5139— GitLab Plugin Allows Non-Admin Users to Modify Default Instance Configuration
Possible ATT&CK Techniques 1AI
T1136.001 · Local AccountAffected Version Matrix 9
| Vendor | Product | Version Range | Status |
|---|---|---|---|
| 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-2026-5139
Vulnerability Information
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Vulnerability Title
GitLab Plugin Allows Non-Admin Users to Modify Default Instance Configuration
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 enforce administrator authorization on the {{setDefaultInstance}} call within the {{/gitlab connect}} command handler, which allows any authenticated user to overwrite the global default GitLab instance configuration via the {{/gitlab connect <instance-name>}} slash command.. Mattermost Advisory ID: MMSA-2026-00644
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L
Source: CVE Program / CVE List V5
Vulnerability Type
授权机制缺失
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，该漏洞源于未在{{/gitlab connect}}命令处理程序中对{{setDefaultInstance}}调用强制执行管理员授权，可能导致任何经过身份验证的用户通过{{/gitlab connect <instance-name>}}斜杠命令覆盖全局默认GitLab实例配置。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
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-2026-5139
| # | POC Description | Source Link | Shenlong Link |
|---|
AI-Generated POCPremium
No public POC found.
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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-2026-6673 | 6.4 MEDIUM | Mattermost Jira plugin had unauthenticated {{/ac/installed}} lifecycle callback during pen |
| 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 |
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V. Comments for CVE-2026-5139
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