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

> CVE-2026-19603: Private channel ID disclosure via user status endpoints. CVSS 4.3 (CVSS 3.1).

Canonical: https://rewindex.com/cve/CVE-2026-19603
Last updated: 2026-10-16T19:23:18Z

- Published: 2026-10-16 07:02 UTC · Updated: 2026-10-16 19:23 UTC · Assigner: Mattermost
- CVSS: 4.3 (CVSS 3.1) · Severity: Medium · Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
- EPSS: 0.18%, 7th percentile (scored 2026-10-25)
- CISA KEV: no
- CWE: CWE-201

## 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

## Affected vendors and products

- Mattermost: Mattermost

## Tracked companies

- [Mattermost](https://rewindex.com/company/mattermost.md)

## References

- [CVE record on cve.org](https://www.cve.org/CVERecord?id=CVE-2026-19603)
- [NVD entry](https://nvd.nist.gov/vuln/detail/CVE-2026-19603)
- [https://mattermost.com/security-updates](https://mattermost.com/security-updates)

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_Sources: CVE records from the CVE Program (cve.org). CVE® is a registered trademark of The MITRE Corporation. (https://www.cve.org/) This product uses data from the NVD API but is not endorsed or certified by the NVD. (https://nvd.nist.gov/) Known Exploited Vulnerabilities catalog from CISA. (https://www.cisa.gov/known-exploited-vulnerabilities-catalog) EPSS scores from FIRST (Exploit Prediction Scoring System). (https://www.first.org/epss/)_


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Canonical: https://rewindex.com/cve/CVE-2026-19603 · Markdown: https://rewindex.com/cve/CVE-2026-19603.md · JSON: https://rewindex.com/api/v1/cves/CVE-2026-19603 · Data licensed CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/) · Generated 2026-10-26T03:12:59.497Z