CVE-2026-15754

EUVD-2026-60212

17.08.2026, 15:16

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

Provider	Type	Base Score	Atk. Vector	Atk. Complexity	Priv. Required	Vector
Mattermost	CNA	4.2 MEDIUM	NETWORK	HIGH	HIGH	CVSS:3.1/AV:N/AC:H/PR:H/UI:R/S:U/C:N/I:H/A:N

Base Score

CVSS 3.x

EPSS Score

Percentile: Unknown

Early Detection

Affected products identified ahead of NVD analysis through intelligence sources.

Vendor	Product	Version	Source
mattermost	mattermost	11.7.0 ≤ 𝑥 ≤ 11.7.6	CNA
mattermost	mattermost	11.8.0 ≤ 𝑥 ≤ 11.8.3	CNA

Common Weakness Enumeration

CWE-863 - Incorrect Authorization
The software performs an authorization check when an actor attempts to access a resource or perform an action, but it does not correctly perform the check. This allows attackers to bypass intended access restrictions.

References

https://mattermost.com/security-updates