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CVE-2026-9812— Missing property field ownership validation in Playbooks run property update endpoint

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 在以下版本中存在漏洞：11.9.x ≤ 11.9.0、11.8.x ≤ 11.8.4、11.7.x ≤ 11.7.7 以及 10.11.x ≤ 10.11.22。 这些版本在更新属性值之前，未能校验该属性字段是否属于指定的 run（运行实例）。这使得拥有 run 属性管理权限的已认证用户能够通过发送引用了其他 run 的属性字段的 REST 请求，导致 Playbooks 插件崩溃。 Mattermost 安全公告 ID：MMSA-2026-00684

CVSS 6.5 · Medium

Possible ATT&CK Techniques 1 AI

T1210.004
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I. Basic Information for CVE-2026-9812

Vulnerability Information
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Vulnerability Title
Missing property field ownership validation in Playbooks run property update endpoint
Source: CVE Program / CVE List V5
Vulnerability Description
Mattermost versions 11.9.x <= 11.9.0, 11.8.x <= 11.8.4, 11.7.x <= 11.7.7, 10.11.x <= 10.11.22 fail to validate that a property field belongs to the specified run before updating its value which allows an authenticated user with run property-management access to crash the Playbooks plugin via a REST request referencing a property field that belongs to a different run. Mattermost Advisory ID: MMSA-2026-00684
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
通过用户控制密钥绕过授权机制
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
Mattermost Mattermost 11.9.0 ~ 11.9.0 -

II. Public POCs for CVE-2026-9812

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III. Intelligence Information for CVE-2026-9812

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Same Patch Batch · Mattermost · 2026-09-14 · 11 CVEs total

CVE-2026-8821 7.1 HIGH Playbooks run owner channel membership permission bypass
CVE-2026-5132 6.5 MEDIUM Unbounded zlib decompression in Calls SDP WebSocket messages
CVE-2026-15814 6.5 MEDIUM Uploading a crafted image causes excessive memory allocation in the Mattermost Server
CVE-2026-10556 5.3 MEDIUM Unauthenticated webhook request with null notification entry could crash the Microsoft Cal
CVE-2026-10542 5.0 MEDIUM Playbooks channel action update validation issue
CVE-2026-13417 4.3 MEDIUM Boards plugin denial of service via unvalidated block fields.properties
CVE-2026-14344 4.3 MEDIUM Inconsistent authorization checks in Mattermost Boards endpoints
CVE-2026-12882 4.3 MEDIUM Mattermost Markdown autolink parsing denial of service
CVE-2026-11993 4.3 MEDIUM Fix authenticated members disabling file content indexing server-wide via extraction pool
CVE-2026-14259 4.3 MEDIUM Board archive import bypasses team board creation permissions

IV. Related Vulnerabilities

Same product: Mattermost
Same vendor: Mattermost
Same weakness: CWE-639

V. Comments for CVE-2026-9812

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