# CVE-2026-6046: Plugin bot username conflict allows user account to be used as bot identity in Mattermost Server

> CVE-2026-6046: Plugin bot username conflict allows user account to be used as bot identity in Mattermost Server. CVSS 5.3 (CVSS 3.1).

Canonical: https://rewindex.com/cve/CVE-2026-6046
Last updated: 2026-06-18T14:33:35Z

- Published: 2026-06-12 15:52 UTC · Updated: 2026-06-18 14:33 UTC · Assigner: Mattermost
- CVSS: 5.3 (CVSS 3.1) · Severity: Medium · Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N
- EPSS: 0.19%, 9th percentile (scored 2026-10-25)
- CISA KEV: no
- CWE: CWE-200

## Description

Mattermost versions 11.6.x \<= 11.6.1, 11.5.x \<= 11.5.4, 10.11.x \<= 10.11.15, 10.11.x \<= 10.11.16 fail to validate that a username returned during bot registration belongs to a bot account, which allows an unprivileged attacker to intercept private messages sent by plugins via direct message channels by pre-registering a user account with a predictable plugin bot username.. Mattermost Advisory ID: MMSA-2026-00649

## 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-2026-6046)
- [NVD entry](https://nvd.nist.gov/vuln/detail/CVE-2026-6046)
- [https://mattermost.com/security-updates](https://mattermost.com/security-updates)

---

_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/)_


---
Canonical: https://rewindex.com/cve/CVE-2026-6046 · Markdown: https://rewindex.com/cve/CVE-2026-6046.md · JSON: https://rewindex.com/api/v1/cves/CVE-2026-6046 · Data licensed CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/) · Generated 2026-10-26T04:03:27.058Z