# CVE-2026-93849: Mattermost allows authenticated users to trigger excessive memory allocation via crafted msgpack binary WebSocket frames

> CVE-2026-93849: Mattermost allows authenticated users to trigger excessive memory allocation via crafted msgpack binary WebSocket frames. CVSS 6.5 (CVSS 3.1).

Canonical: https://rewindex.com/cve/CVE-2026-93849
Last updated: 2026-11-02T18:39:05Z

- Published: 2026-10-26 14:25 UTC · Updated: 2026-11-02 18:39 UTC · Assigner: Mattermost
- CVSS: 6.5 (CVSS 3.1) · Severity: Medium · Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
- EPSS: 0.47%, 41th percentile (scored 2026-11-03)
- CISA KEV: no
- CWE: CWE-789

## 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 Mattermost fail to apply allocation limits to the byte-string decode paths in its WebSocket msgpack decoder, which allows an authenticated remote attacker to cause excessive server memory allocation via a crafted binary WebSocket frame declaring a Bin32 payload length of up to 4,294,967,295 bytes.. Mattermost Advisory ID: MMSA-2026-00768

## 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-2026-93849)
- [NVD entry](https://nvd.nist.gov/vuln/detail/CVE-2026-93849)
- [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-2026-93849 · Markdown: https://rewindex.com/cve/CVE-2026-93849.md · JSON: https://rewindex.com/api/v1/cves/CVE-2026-93849 · Data licensed CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/) · Generated 2026-11-04T15:19:36.256Z