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Vulnerability record · CVE-2026-16047 · published 17 August 2026

CVE-2026-16047: Mattermost server missing authorization vulnerability

Mattermost · Mattermost Server

Mattermost versions 11.7.x <= 11.7.6, 10.11.x <= 10.11.21, 11.8.x <= 11.8.3 fail to validate that users have read access to a channel before linking a board to it, which allows an authenticated attacker to discover the membership of private channels on the same team via creating, patching, importing, or bulk-creating boards with an arbitrary channelId. Mattermost Advisory ID: MMSA-2026-00674

4.3 CVSS 3.1 Medium EPSS 0.27% · top 82.8% CWE-862 · Missing authorization
4.3CVSS 3.1 base score
0.27%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
1References
18 Aug 2026Last modified by NVD

Description

Mattermost versions 11.7.x <= 11.7.6, 10.11.x <= 10.11.21, 11.8.x <= 11.8.3 fail to validate that users have read access to a channel before linking a board to it, which allows an authenticated attacker to discover the membership of private channels on the same team via creating, patching, importing, or bulk-creating boards with an arbitrary channelId. Mattermost Advisory ID: MMSA-2026-00674

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

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://mattermost.com/security-updates Vendor Advisory

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

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Source: NIST National Vulnerability Database (record CVE-2026-16047), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.