CVE-2026-3473Improper file ownership validation in the Boards API allows unauthorised file access
- 5.9MediumCVSS base score
- 0.15%Exploitation in 30 daysEPSS · top 96% of all CVEs
- NoKnown exploitednot in CISA's KEV catalog
- NonePublic exploitsnone known yet
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
Timeline
ID reserved
By Mattermost
- 3 months later
· 3 months later
Published
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| MattermostCNA (assigner) | 3.1 | Medium5.9 | CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:L/A:N |
| NVDNVD · Analyzed | 3.1 | High7.1 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:N |
- EPSS (exploitation in 30 days)
- 0.15% · top 96% of all CVEs (12 Nov 2026)
- CISA SSVC
- Exploitation: none · Automatable: no · Technical impact: partial
The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 5.9.
Affected products
- affected 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
- unaffected 11.7.0
- unaffected 11.6.1
- unaffected 11.5.4
- unaffected 11.4.5
- unaffected 10.11.15
Affected packages
From reviewed advisories of the GitHub Advisory Database.
- Gogithub.com/mattermost/mattermost-serverGHSA-7pf2-9c95-w332 (opens in a new tab)
What to do
Solution: Update Mattermost to versions 11.7.0, 11.6.1, 11.5.4, 11.4.5, 10.11.15 or higher.
References
References1
- MMSA-2026-00620 (opens in a new tab)vendor-advisory
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- EUVD EUVD-2026-31429 (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisory GHSA-7pf2-9c95-w332 (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://cveledger.app/cve/CVE-2026-3473)Record last updated .