CVE-2026-28759 - NVD | ByteOS Network

NVD Vulnerability Details :

CVE-2026-28759

Analyzed

More Info Official Page

Source-responsibledisclosure@mattermost.com

Published At-18 May, 2026 | 08:16

Updated At-18 May, 2026 | 19:17

Mattermost versions 11.5.x <= 11.5.1, 10.11.x <= 10.11.13, 11.4.x <= 11.4.3 fail to validate that a remote cluster has access to a channel before processing membership removal requests during shared channel membership sync, which allows a malicious remote cluster to remove any user from any channel, including private channels, via crafted membership sync messages targeting channels the remote cluster is not authorized to access. Mattermost Advisory ID: MMSA-2026-00576

Metrics

Type	Version	Base score	Base severity	Vector
Secondary	3.1	4.3	MEDIUM	CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N

Type: Secondary

Version: 3.1

Base score: 4.3

Base severity: MEDIUM

Vector:

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

CPE Matches

Mattermost, Inc.

>>mattermost_server>>Versions from 10.11.0(inclusive) to 10.11.14(exclusive)

cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*

Mattermost, Inc.

>>mattermost_server>>Versions from 11.4.0(inclusive) to 11.4.4(exclusive)

cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*

Mattermost, Inc.

>>mattermost_server>>Versions from 11.5.0(inclusive) to 11.5.2(exclusive)

cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*

Weaknesses

CWE ID	Type	Source
CWE-863	Secondary	responsibledisclosure@mattermost.com

CWE ID: CWE-863

Type: Secondary

Source: responsibledisclosure@mattermost.com

References

Hyperlink	Source	Resource
https://mattermost.com/security-updates	responsibledisclosure@mattermost.com	Vendor Advisory

Hyperlink: https://mattermost.com/security-updates

Source: responsibledisclosure@mattermost.com

Resource:

Vendor Advisory