# CVE-2026-96259: Mattermost server-side request forgery via OAuth endpoints configurable by a System Administrator

> CVE-2026-96259: Mattermost server-side request forgery via OAuth endpoints configurable by a System Administrator. CVSS 5.5 (CVSS 3.1).

Canonical: https://rewindex.com/cve/CVE-2026-96259
Last updated: 2026-10-07T16:41:14Z

- Published: 2026-09-22 20:34 UTC · Updated: 2026-10-07 16:41 UTC · Assigner: Mattermost
- CVSS: 5.5 (CVSS 3.1) · Severity: Medium · Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:L/I:L/A:N
- EPSS: 0.26%, 17th percentile (scored 2026-10-25)
- CISA KEV: no
- CWE: CWE-918

## 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 apply the internal-connection filter to OAuth endpoint requests, which allows a System Administrator to make the server issue requests to internal network addresses and read the responses via the configured OAuth token and userinfo endpoints.. Mattermost Advisory ID: MMSA-2026-00776

## 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-2026-96259)
- [NVD entry](https://nvd.nist.gov/vuln/detail/CVE-2026-96259)
- [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-2026-96259 · Markdown: https://rewindex.com/cve/CVE-2026-96259.md · JSON: https://rewindex.com/api/v1/cves/CVE-2026-96259 · Data licensed CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/) · Generated 2026-10-26T02:51:40.648Z