CVE-2026-4635

Persistent notification timing attack causing server denial of service

CVSS 6.5 MEDIUMEPSS 0.2%CWE-362

Vexday Risk Score

13Low

SSVC decision (CISA)

Track

No exploitation signal → monitor

CVSS 6.5EPSS 0.2%KEV nãoPoC —Nuclei —Metasploit —Patch referenciado

Lifecycle

22 May 2026Published on NVD

Recommendation: Monitor — no exploitation signal at the moment.

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

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Affected products

Mattermost · Mattermost

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References

https://mattermost.com/security-updates