CVE-2026-3473 - Vulnerability Details - OpenCVE

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

No CVSS v4.0

Attack Vector Network

Attack Complexity High

Privileges Required Low

Scope Unchanged

Confidentiality Impact High

Integrity Impact Low

Availability Impact None

User Interaction None

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

The EPSS score is 0.00028.

Exploitation none

Automatable no

Technical Impact partial

Vendors	Products
Mattermost	Mattermost

No data.

No data.

OpenCVE Enrichment is a feature of OpenCVE that uses AI to automatically link vendors and products to CVEs. Learn more on GitHub.

Vendors	Products
Mattermost	Mattermost

References

Link	Providers
https://mattermost.com/security-updates

History

Fri, 22 May 2026 13:45:00 +0000

Type	Values Removed	Values Added
First Time appeared		Mattermost Mattermost mattermost
Vendors & Products		Mattermost Mattermost mattermost

Fri, 22 May 2026 13:30:00 +0000

Type	Values Removed	Values Added
Metrics		ssvc `{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}`

Fri, 22 May 2026 11:00:00 +0000

Type	Values Removed	Values Added
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
Title		Improper file ownership validation in the Boards API allows unauthorised file access
Weaknesses		CWE-639
References		https://mattermost.com/security-updates
Metrics		cvssV3_1 `{'score': 5.9, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:L/A:N'}`

MITRE

Status: PUBLISHED

Assigner: Mattermost

Published: 2026-05-22T10:27:02.600Z

Updated: 2026-05-22T12:12:49.437Z

Reserved: 2026-03-03T12:57:13.379Z

Link: CVE-2026-3473

Vulnrichment

Updated: 2026-05-22T12:12:45.995Z

NVD

No data.

Redhat

No data.

OpenCVE Enrichment

Updated: 2026-05-22T13:30:35Z

{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-3473", "assignerOrgId": "9302f53e-dde5-4bf3-b2f2-a83f91ac0eee", "state": "PUBLISHED", "assignerShortName": "Mattermost", "dateReserved": "2026-03-03T12:57:13.379Z", "datePublished": "2026-05-22T10:27:02.600Z", "dateUpdated": "2026-05-22T12:12:49.437Z"}, "containers": {"cna": {"affected": [{"defaultStatus": "unaffected", "product": "Mattermost", "vendor": "Mattermost", "versions": [{"lessThanOrEqual": "11.6.0", "status": "affected", "version": "11.6.0", "versionType": "semver"}, {"lessThanOrEqual": "11.5.3", "status": "affected", "version": "11.5.0", "versionType": "semver"}, {"lessThanOrEqual": "11.4.4", "status": "affected", "version": "11.4.0", "versionType": "semver"}, {"lessThanOrEqual": "10.11.14", "status": "affected", "version": "10.11.0", "versionType": "semver"}, {"version": "11.7.0", "status": "unaffected"}, {"version": "11.6.1", "status": "unaffected"}, {"version": "11.5.4", "status": "unaffected"}, {"version": "11.4.5", "status": "unaffected"}, {"version": "10.11.15", "status": "unaffected"}]}], "credits": [{"lang": "en", "type": "finder", "value": "eahmed"}], "descriptions": [{"lang": "en", "value": "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"}], "metrics": [{"cvssV3_1": {"attackVector": "NETWORK", "attackComplexity": "HIGH", "privilegesRequired": "LOW", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "LOW", "availabilityImpact": "NONE", "version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:L/A:N", "baseSeverity": "MEDIUM", "baseScore": 5.9}, "format": "CVSS", "scenarios": [{"lang": "en", "value": "GENERAL"}]}], "problemTypes": [{"descriptions": [{"lang": "en", "type": "CWE", "description": "CWE-639: Authorization Bypass Through User-Controlled Key", "cweId": "CWE-639"}]}], "references": [{"url": "https://mattermost.com/security-updates", "name": "MMSA-2026-00620", "tags": ["vendor-advisory"]}], "solutions": [{"value": "Update Mattermost to versions 11.7.0, 11.6.1, 11.5.4, 11.4.5, 10.11.15 or higher.", "lang": "en"}], "source": {"advisory": "MMSA-2026-00620", "defect": ["https://mattermost.atlassian.net/browse/MM-67759"], "discovery": "EXTERNAL"}, "title": "Improper file ownership validation in the Boards API allows unauthorised file access", "providerMetadata": {"orgId": "9302f53e-dde5-4bf3-b2f2-a83f91ac0eee", "shortName": "Mattermost", "dateUpdated": "2026-05-22T10:27:02.600Z"}, "x_generator": {"engine": "cvelib 1.8.0"}}, "adp": [{"metrics": [{"other": {"type": "ssvc", "content": {"timestamp": "2026-05-22T12:12:41.198607Z", "id": "CVE-2026-3473", "options": [{"Exploitation": "none"}, {"Automatable": "no"}, {"Technical Impact": "partial"}], "role": "CISA Coordinator", "version": "2.0.3"}}}], "title": "CISA ADP Vulnrichment", "providerMetadata": {"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-05-22T12:12:49.437Z"}}]}}

{"dataType": "CVE_RECORD", "containers": {"adp": [{"title": "CISA ADP Vulnrichment", "metrics": [{"other": {"type": "ssvc", "content": {"id": "CVE-2026-3473", "role": "CISA Coordinator", "options": [{"Exploitation": "none"}, {"Automatable": "no"}, {"Technical Impact": "partial"}], "version": "2.0.3", "timestamp": "2026-05-22T12:12:41.198607Z"}}}], "providerMetadata": {"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-05-22T12:12:45.995Z"}}], "cna": {"title": "Improper file ownership validation in the Boards API allows unauthorised file access", "source": {"defect": ["https://mattermost.atlassian.net/browse/MM-67759"], "advisory": "MMSA-2026-00620", "discovery": "EXTERNAL"}, "credits": [{"lang": "en", "type": "finder", "value": "eahmed"}], "metrics": [{"format": "CVSS", "cvssV3_1": {"scope": "UNCHANGED", "version": "3.1", "baseScore": 5.9, "attackVector": "NETWORK", "baseSeverity": "MEDIUM", "vectorString": "CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:L/A:N", "integrityImpact": "LOW", "userInteraction": "NONE", "attackComplexity": "HIGH", "availabilityImpact": "NONE", "privilegesRequired": "LOW", "confidentialityImpact": "HIGH"}, "scenarios": [{"lang": "en", "value": "GENERAL"}]}], "affected": [{"vendor": "Mattermost", "product": "Mattermost", "versions": [{"status": "affected", "version": "11.6.0", "versionType": "semver", "lessThanOrEqual": "11.6.0"}, {"status": "affected", "version": "11.5.0", "versionType": "semver", "lessThanOrEqual": "11.5.3"}, {"status": "affected", "version": "11.4.0", "versionType": "semver", "lessThanOrEqual": "11.4.4"}, {"status": "affected", "version": "10.11.0", "versionType": "semver", "lessThanOrEqual": "10.11.14"}, {"status": "unaffected", "version": "11.7.0"}, {"status": "unaffected", "version": "11.6.1"}, {"status": "unaffected", "version": "11.5.4"}, {"status": "unaffected", "version": "11.4.5"}, {"status": "unaffected", "version": "10.11.15"}], "defaultStatus": "unaffected"}], "solutions": [{"lang": "en", "value": "Update Mattermost to versions 11.7.0, 11.6.1, 11.5.4, 11.4.5, 10.11.15 or higher."}], "references": [{"url": "https://mattermost.com/security-updates", "name": "MMSA-2026-00620", "tags": ["vendor-advisory"]}], "x_generator": {"engine": "cvelib 1.8.0"}, "descriptions": [{"lang": "en", "value": "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"}], "problemTypes": [{"descriptions": [{"lang": "en", "type": "CWE", "cweId": "CWE-639", "description": "CWE-639: Authorization Bypass Through User-Controlled Key"}]}], "providerMetadata": {"orgId": "9302f53e-dde5-4bf3-b2f2-a83f91ac0eee", "shortName": "Mattermost", "dateUpdated": "2026-05-22T10:27:02.600Z"}}}, "cveMetadata": {"cveId": "CVE-2026-3473", "state": "PUBLISHED", "dateUpdated": "2026-05-22T12:12:49.437Z", "dateReserved": "2026-03-03T12:57:13.379Z", "assignerOrgId": "9302f53e-dde5-4bf3-b2f2-a83f91ac0eee", "datePublished": "2026-05-22T10:27:02.600Z", "assignerShortName": "Mattermost"}, "dataVersion": "5.2"}