Not a U.S. government website. NDD is an independent vulnerability database by Volerion and is not affiliated with or endorsed by NIST or NVD.

CVE-2026-19603 Details

Description

Mattermost versions 11.9.x <= 11.9.1, 11.8.x <= 11.8.5, 11.7.x <= 11.7.10, 11.10.x <= 11.10.1 fail to sanitize the active channel field returned by the user status API endpoints, which allows an authenticated user to learn the channel ID of a private channel another user is actively viewing via the status endpoints, without being a member of that channel. Mattermost Advisory ID: MMSA-2026-00765

Metrics

CVSS 3.x Severity and Vector Strings:

CNA: [email protected]CVSS-B:4.3 MEDIUMVector:CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N

References to Advisories, Solutions, and Tools

By selecting these links, you will be leaving this site. These are references gathered from the official CVE record and are not endorsed by Volerion.

URL	Source(s)	Tag(s)
https://mattermost.com/security-updates	[email protected]	Vendor Advisory

Weakness Enumeration

CWE-ID	CWE Name	Source
CWE-201	Insertion of Sensitive Information Into Sent Data	[email protected]

Affected Products

Product	Versions
mattermost mattermost server	>= 11.7.0, < 11.7.11 >= 11.8.0, < 11.8.6 >= 11.9.0, < 11.9.2 >= 11.10.0, < 11.10.2
CPE cpe:2.3:a:mattermost:mattermost_server:::::::: Remediation No remediation found in references.

Change History

3 change records found show changes

Date	Action	Recorded By
Oct 29, 2026	Initial Analysis	[email protected]
Oct 16, 2026	CVE Modified	CISA-ADP
Oct 16, 2026	New CVE Received	[email protected]