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CVE-2026-4055— Insufficient permission validation on cross-team playbook run creation

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公司的一个开源协作平台。 Mattermost 11.5.1及之前的11.5.x版本存在安全漏洞，该漏洞源于未能验证针对目标团队的团队级运行创建权限，可能导致经过身份验证的团队成员在缺乏权限的团队中创建运行。

CVSS 4.3 · Medium EPSS 0.15% · P5

Possible ATT&CK Techniques 1 AI

T1136.002 · Domain Account

Affected Version Matrix 5

VendorProduct Version RangeStatus
Mattermost Mattermost 11.5.0≤ 11.5.1 affected
11.6.0 unaffected
11.5.2 unaffected
10.11.14 unaffected
11.4.4 unaffected
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I. Basic Information for CVE-2026-4055

Vulnerability Information
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Vulnerability Title
Insufficient permission validation on cross-team playbook run creation
Source: CVE Program / CVE List V5
Vulnerability Description
Mattermost versions 11.5.x <= 11.5.1 fail to validate team-level run_create permission against the target team when creating a playbook run which allows an authenticated team member to create runs in teams where they lack permission via specifying a different team ID in the run creation API request. Mattermost Advisory ID: MMSA-2026-00629
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:N
Source: CVE Program / CVE List V5
Vulnerability Type
授权机制不正确
Source: CVE Program / CVE List V5
Vulnerability Title
Mattermost 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Mattermost是美国Mattermost公司的一个开源协作平台。 Mattermost 11.5.1及之前的11.5.x版本存在安全漏洞，该漏洞源于未能验证针对目标团队的团队级运行创建权限，可能导致经过身份验证的团队成员在缺乏权限的团队中创建运行。
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 11.5.0 ~ 11.5.1 -

II. Public POCs for CVE-2026-4055

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III. Intelligence Information for CVE-2026-4055

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Same Patch Batch · Mattermost · 2026-05-21 · 3 CVEs total

CVE-2026-4858 8.0 HIGH Path traversal in integration action URL leading to arbitrary API execution via system adm
CVE-2026-22880 6.1 MEDIUM Mobile SSO authentication flow allows credential theft via malicious server

IV. Related Vulnerabilities

Same product: Mattermost
Same vendor: Mattermost
Same weakness: CWE-863

V. Comments for CVE-2026-4055

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