CVE-2026-19603 — Private channel ID disclosure via user status endpoints

Description (CNA)

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

Affected (CNA)

Vendor / product	Versions
Mattermost / Mattermost	affected 11.9.0 through 11.9.1; affected 11.8.0 through 11.8.5; affected 11.7.0 through 11.7.10; affected 11.10.0 through 11.10.1; unaffected 11.11.0; unaffected 11.9.2; unaffected 11.8.6; unaffected 11.7.11; unaffected 11.10.2

CWE

CWE-201

References

https://mattermost.com/security-updates

ADP enrichment

CISA-ADP

No English description supplied.

No references supplied.