CVE-2026-19603

MediumCVSS 4.3/10Last modified Oct 29, 2026

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 3.1 4.3/10CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N

Weakness enumeration

CWE-201

Affected software

Vendor	Product	Versions
Mattermost	Mattermost	>= 11.9.0, <= 11.9.1; >= 11.8.0, <= 11.8.5; >= 11.7.0, <= 11.7.10; >= 11.10.0, <= 11.10.1

References

https://mattermost.com/security-updatesVendor Advisory

Timeline

Published: Oct 16, 2026
Last modified: Oct 29, 2026
NVD status: Analyzed

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