CVE-2026-3473— Improper file ownership validation in the Boards API allows unauthorised file access
Possible ATT&CK Techniques 1AI
T1530 · Data from Cloud StorageAffected Version Matrix 9
| Vendor | Product | Version Range | Status |
|---|---|---|---|
| Mattermost | Mattermost | 11.6.0≤ 11.6.0 | affected |
11.5.0≤ 11.5.3 | affected | ||
11.4.0≤ 11.4.4 | affected | ||
10.11.0≤ 10.11.14 | affected | ||
11.7.0 | unaffected | ||
11.6.1 | unaffected | ||
11.5.4 | unaffected | ||
11.4.5 | unaffected | ||
| … +1 more rows | |||
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I. Basic Information for CVE-2026-3473
Vulnerability Information
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Vulnerability Title
Improper file ownership validation in the Boards API allows unauthorised file access
Source: NVD (National Vulnerability Database)
Vulnerability Description
Mattermost versions 11.6.x <= 11.6.0, 11.5.x <= 11.5.3, 11.4.x <= 11.4.4, 10.11.x <= 10.11.14 fail to validate file ownership and access control, which allows an authenticated user to access and download files belonging to other users or teams via crafted Boards API requests using valid file IDs.. Mattermost Advisory ID: MMSA-2026-00620
Source: NVD (National Vulnerability Database)
CVSS Information
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:L/A:N
Source: NVD (National Vulnerability Database)
Vulnerability Type
通过用户控制密钥绕过授权机制
Source: NVD (National Vulnerability Database)
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 11.6.0及之前的11.6.x版本、11.5.3及之前的11.5.x版本、11.4.4及之前的11.4.x版本和10.11.14及之前的10.11.x版本存在安全漏洞，该漏洞源于未能验证文件所有权和访问控制，可能导致认证用户通过特制的Boards API请求使用有效文件ID访问和下载属于其他用户或团队的文件。
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 | 11.6.0 ~ 11.6.0 | - |
II. Public POCs for CVE-2026-3473
| # | POC Description | Source Link | Shenlong Link |
|---|
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Same Patch Batch · Mattermost · 2026-05-22 · 8 CVEs total
| CVE-2026-5740 | 7.5 HIGH | Unauthenticated WebSocket binary frame causes denial of service in Mattermost Server |
| CVE-2026-4635 | 6.5 MEDIUM | Persistent notification timing attack causing server denial of service |
| CVE-2026-5755 | 6.5 MEDIUM | Denial of service via crafted TIFF file upload |
| CVE-2026-28735 | 5.4 MEDIUM | GitHub OAuth Scope Validation |
| CVE-2026-5308 | 4.9 MEDIUM | Missing request body size limits on Zoom plugin HTTP endpoints |
| CVE-2026-4646 | 4.3 MEDIUM | Insufficient input validation in GitHub plugin API causes denial of service |
| CVE-2026-3636 | 4.3 MEDIUM | Sanitize team member data returned by API |
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Same vendor: Mattermost
- CVE-2026-6961
CVE-2026-6961: Path traversal via unsanitized FileInfo.Name - CVE-2026-7387
Mattermost group syncable endpoints allow privilege escalati - CVE-2026-6046
Plugin bot username conflict allows user account to be used - CVE-2026-6689
*Missing* {{invite_user}} *permission check on team creation - CVE-2026-7184
Mattermost Remote Cluster PATCH API Leaks Authentication Tok
Same weakness: CWE-639
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V. Comments for CVE-2026-3473
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