Improper file ownership validation in the Boards API allows unauthorised file access
Summary
| CVE | CVE-2026-3473 |
|---|---|
| State | PUBLISHED |
| Assigner | Mattermost |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-05-22 11:16:22 UTC |
| Updated | 2026-07-23 16:10:00 UTC |
| 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 |
Risk And Classification
Primary CVSS: v3.1 7.1 HIGH from [email protected]
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:N
Problem Types: CWE-639 | CWE-639 CWE-639: Authorization Bypass Through User-Controlled Key
| Version | Source | Type | Score | Severity | Vector |
|---|---|---|---|---|---|
| 3.1 | [email protected] | Primary | 7.1 | HIGH | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:N |
| 3.1 | [email protected] | Secondary | 5.9 | MEDIUM | CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:L/A:N |
| 3.1 | CNA | CVSS | 5.9 | MEDIUM | CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:L/A:N |
CVSS v3.1 Breakdown
Attack Vector
NetworkAttack Complexity
LowPrivileges Required
LowUser Interaction
NoneScope
UnchangedConfidentiality
HighIntegrity
LowAvailability
NoneCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:N
NVD Known Affected Configurations (CPE 2.3)
| Type | Vendor | Product | Version | Update | Edition | Language |
|---|---|---|---|---|---|---|
| Application | Mattermost | Mattermost Server | All | All | All | All |
Vendor Declared Affected Products
| Source | Vendor | Product | Version | Platforms |
|---|---|---|---|---|
| CNA | Mattermost | Mattermost | affected 11.6.0 11.6.0 semver | Not specified |
| CNA | Mattermost | Mattermost | affected 11.5.0 11.5.3 semver | Not specified |
| CNA | Mattermost | Mattermost | affected 11.4.0 11.4.4 semver | Not specified |
| CNA | Mattermost | Mattermost | affected 10.11.0 10.11.14 semver | Not specified |
| CNA | Mattermost | Mattermost | unaffected 11.7.0 | Not specified |
| CNA | Mattermost | Mattermost | unaffected 11.6.1 | Not specified |
| CNA | Mattermost | Mattermost | unaffected 11.5.4 | Not specified |
| CNA | Mattermost | Mattermost | unaffected 11.4.5 | Not specified |
| CNA | Mattermost | Mattermost | unaffected 10.11.15 | Not specified |
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| mattermost.com/security-updates | [email protected] | mattermost.com | Vendor Advisory |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
Vendor Comments And Credit
Discovery Credit
CNA: eahmed (en)
Additional Advisory Data
Solutions
CNA: Update Mattermost to versions 11.7.0, 11.6.1, 11.5.4, 11.4.5, 10.11.15 or higher.
There are currently no legacy QID mappings associated with this CVE.