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

Description (CNA)

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 (CNA)

Vendor / product	Versions
Mattermost / Mattermost	affected 11.6.0 through 11.6.0; affected 11.5.0 through 11.5.3; affected 11.4.0 through 11.4.4; affected 10.11.0 through 10.11.14; unaffected 11.7.0; unaffected 11.6.1; unaffected 11.5.4; unaffected 11.4.5; unaffected 10.11.15

CWE

CWE-362

References

https://mattermost.com/security-updates

ADP enrichment

CISA-ADP

No English description supplied.

No references supplied.