CVE-2026-19603

EUVD-2026-102742
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
ProviderTypeBase ScoreAtk. VectorAtk. ComplexityPriv. RequiredVector
MattermostCNA
4.3 MEDIUM
NETWORK
LOW
LOW
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
Base Score
CVSS 3.x
EPSS Score
Percentile: 6.8%
Early Detection
Affected products identified ahead of NVD analysis through intelligence sources.
VendorProductVersionSource
mattermostmattermost
11.9.0 ≤
𝑥
≤ 11.9.1
CNA
mattermostmattermost
11.8.0 ≤
𝑥
≤ 11.8.5
CNA
mattermostmattermost
11.7.0 ≤
𝑥
≤ 11.7.10
CNA
mattermostmattermost
11.10.0 ≤
𝑥
≤ 11.10.1
CNA