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Vulnerability record · CVE-2026-15754 · published 17 August 2026

CVE-2026-15754: Mattermost server incorrect authorization vulnerability

Mattermost · Mattermost Server

Mattermost versions 11.7.x <= 11.7.6, 11.8.x <= 11.8.3 The access control policy unassign endpoint fails to re-validate that each target channel still belongs to the requesting admin's team, which allows an authenticated team administrator to remove ABAC (attribute-based access control) policy assignments from channels outside their team via the policy unassign API after a channel has been moved to another team.. Mattermost Advisory ID: MMSA-2026-00718

4.2 CVSS 3.1 Medium EPSS 0.25% · top 85.8% CWE-863 · Incorrect authorization
4.2CVSS 3.1 base score
0.25%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, 11.8.x <= 11.8.3 The access control policy unassign endpoint fails to re-validate that each target channel still belongs to the requesting admin's team, which allows an authenticated team administrator to remove ABAC (attribute-based access control) policy assignments from channels outside their team via the policy unassign API after a channel has been moved to another team.. Mattermost Advisory ID: MMSA-2026-00718

CVSS:3.1/AV:N/AC:H/PR:H/UI:R/S:U/C:N/I:H/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-2026-15754), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.