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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

PUBLISHED Reserved 2026-03-03 | Published 2026-05-22 | Updated 2026-05-22 | Assigner Mattermost




MEDIUM: 5.9CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:L/A:N

Problem types

CWE-639: Authorization Bypass Through User-Controlled Key

Product status

Default status
unaffected

11.6.0 (semver)
affected

11.5.0 (semver)
affected

11.4.0 (semver)
affected

10.11.0 (semver)
affected

11.7.0
unaffected

11.6.1
unaffected

11.5.4
unaffected

11.4.5
unaffected

10.11.15
unaffected

Credits

eahmed finder

References

mattermost.com/security-updates (MMSA-2026-00620) vendor-advisory

cve.org (CVE-2026-3473)

nvd.nist.gov (CVE-2026-3473)

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