# CVE-2026-4635: Persistent notification timing attack causing server denial of service

> CVE-2026-4635: Persistent notification timing attack causing server denial of service. CVSS 6.5 (CVSS 3.1).

Canonical: https://rewindex.com/cve/CVE-2026-4635
Last updated: 2026-07-23T16:10:00Z

- Published: 2026-05-22 10:28 UTC · Updated: 2026-07-23 16:10 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: 0.17%, 7th percentile (scored 2026-10-25)
- CISA KEV: no
- CWE: CWE-362

## Description

Mattermost versions 11.6.x \<= 11.6.0, 11.5.x \<= 11.5.3, 11.4.x \<= 11.4.4, 10.11.x \<= 10.11.14 fail to archive the channel before removing persistent notifications which allows authenticated user to crash the server via timing the creation of persistent notification message between the server deleting existing persistent notifications and archiving the channel.. Mattermost Advisory ID: MMSA-2026-00637

## 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-2026-4635)
- [NVD entry](https://nvd.nist.gov/vuln/detail/CVE-2026-4635)
- [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-2026-4635 · Markdown: https://rewindex.com/cve/CVE-2026-4635.md · JSON: https://rewindex.com/api/v1/cves/CVE-2026-4635 · Data licensed CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/) · Generated 2026-10-26T02:00:37.163Z