# CVE-2026-18223: Mattermost invitation tokens not bound to invited email address allowing unauthorized team and private channel access

> CVE-2026-18223: Mattermost invitation tokens not bound to invited email address allowing unauthorized team and private channel access. CVSS 5.0 (CVSS 3.1).

Canonical: https://rewindex.com/cve/CVE-2026-18223
Last updated: 2026-10-16T19:23:18Z

- Published: 2026-10-16 07:12 UTC · Updated: 2026-10-16 19:23 UTC · Assigner: Mattermost
- CVSS: 5.0 (CVSS 3.1) · Severity: Medium · Vector: CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:L/A:N
- EPSS: 0.16%, 5th percentile (scored 2026-10-25)
- CISA KEV: no
- CWE: CWE-863

## Description

Mattermost versions 11.10.x \<= 11.10.0, 11.7.x \<= 11.7.9, 11.9.x \<= 11.9.1, 11.8.x \<= 11.8.5 fail to validate the invited recipient's email address when redeeming team and guest invitation tokens, which allows an authenticated attacker to join a team or gain unauthorized access to private channels via a forwarded or leaked invitation link.. Mattermost Advisory ID: MMSA-2026-00747

## 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-2026-18223)
- [NVD entry](https://nvd.nist.gov/vuln/detail/CVE-2026-18223)
- [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-2026-18223 · Markdown: https://rewindex.com/cve/CVE-2026-18223.md · JSON: https://rewindex.com/api/v1/cves/CVE-2026-18223 · Data licensed CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/) · Generated 2026-10-26T03:11:47.502Z