CVE-2026-19603
MEDIUM
CVSS 4.3
Published: 2026-10-16
Modified: 2026-10-16
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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
Quick Facts
| CVE ID | CVE-2026-19603 |
| CVSS Score | 4.3 |
| Vector | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N |
| Published | 2026-10-16 |
| Exploited | No |
| CISA KEV | No |
| PoC | Not public |