CVE-2026-9859 | BDVDB-2026-360413 Detail

MattermostMattermost

Description#

Mattermost versions 11.7.x <= 11.7.6, 10.11.x <= 10.11.21, 11.8.x <= 11.8.3 fail to enforce PermissionManageBoardRoles on the channelId field of the batch endpoint, which allows an authenticated board editor to relink any board they can edit to an arbitrary channel via a crafted PATCH request. Mattermost Advisory ID: MMSA-2026-00686

Impact#

Per CVSS v3.1: confidentiality impact high, integrity impact none, availability impact none. Attack vector: network.

Weaknesses#

CWE-863 Incorrect Authorization

References#

https://mattermost.com/security-updates

Exploit#

No public exploit known

History#

Version 12026-08-17Record published in the CVE List.
Version 22026-08-18Most recent update recorded in the CVE List.

Published

Published: 2026-08-17
Last modified: 2026-08-18

Vendor information

Vendor: Mattermost
Product: Mattermost

All Mattermost vulnerabilities

Score

6.5 Medium

EPSS

less than 1%, Very Low

Estimated chance of exploitation in the next 30 days. EPSS percentile: 27.7.

KEV

Not listed in the CISA Known Exploited Vulnerabilities catalog.

Impact

Incorrect Authorization

Action

No specific action is recorded in the source data. Check the references for vendor guidance.

Affected Systems

Vulnerable
>= 11.7.0 and <= 11.7.6
Fixed
Not stated
Vulnerable
>= 10.11.0 and <= 10.11.21
Fixed
Not stated
Vulnerable
>= 11.8.0 and <= 11.8.3
Fixed
Not stated
Vulnerable
Not stated
Fixed
11.9.0
Vulnerable
Not stated
Fixed
11.7.7
Vulnerable
Not stated
Fixed
10.11.22
Vulnerable
Not stated
Fixed
11.8.4

Scoring System

CVSS v4.0

Not available

CVSS v3.1

6.5 Medium

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

Metric breakdown
Attack Vector	Network
Attack Complexity	Low
Privileges Required	Low
User Interaction	None
Scope	Unchanged
Confidentiality	High
Integrity	None
Availability	None

CVSS v3.0

Not available

CVSS v2

Not available

Source: CVE List v5 (record); CISA KEV (kev, action); FIRST EPSS (epss).