# CVE-2026-10103: Authenticated remote cluster can modify or delete posts it does not own in Mattermost Connected Workspaces shared channels

> CVE-2026-10103: Authenticated remote cluster can modify or delete posts it does not own in Mattermost Connected Workspaces shared channels. CVSS 4.3 (CVSS 3.1).

Canonical: https://rewindex.com/cve/CVE-2026-10103
Last updated: 2026-07-14T15:16:54Z

- Published: 2026-07-13 07:57 UTC · Updated: 2026-07-14 15:16 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:N/I:L/A:N
- EPSS: 0.24%, 15th percentile (scored 2026-10-25)
- CISA KEV: no
- CWE: CWE-639

## Description

Mattermost versions 11.7.x \<= 11.7.2, 11.6.x \<= 11.6.4, 10.11.x \<= 10.11.19 fail to verify post ownership in the shared channel inbound sync handler, which allows an authenticated remote cluster to modify or delete posts authored by local users or other remotes via crafted sync messages referencing arbitrary post IDs in channels shared with that remote.. Mattermost Advisory ID: MMSA-2026-00689

## 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-2026-10103)
- [NVD entry](https://nvd.nist.gov/vuln/detail/CVE-2026-10103)
- [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-2026-10103 · Markdown: https://rewindex.com/cve/CVE-2026-10103.md · JSON: https://rewindex.com/api/v1/cves/CVE-2026-10103 · Data licensed CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/) · Generated 2026-10-26T02:13:35.038Z