CVE-2026-91181

EUVD-2026-78160

14.09.2026, 22:16

Mattermost versions 11.9.x <= 11.9.0, 11.8.x <= 11.8.4, 11.7.x <= 11.7.7, 10.11.x <= 10.11.22 Fail to sanitize Team objects returned by the data retention teams endpoint which allows an authenticated user holding only the read-only Data Retention Policy permission to obtain a private team's secret invite_id and email, and use it to join the team without authorization, via GET /api/v4/data_retention/policies/{policy_id}/teams.. Mattermost Advisory ID: MMSA-2026-00702

Provider	Type	Base Score	Atk. Vector	Atk. Complexity	Priv. Required	Vector
Mattermost	CNA	6.5 MEDIUM	NETWORK	LOW	HIGH	CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/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	𝑥 ≤ 11.9.0	CNA
mattermost	mattermost	11.8.0 ≤ 𝑥 ≤ 11.8.4	CNA
mattermost	mattermost	11.7.0 ≤ 𝑥 ≤ 11.7.7	CNA
mattermost	mattermost	10.11.0 ≤ 𝑥 ≤ 10.11.22	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