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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

PUBLISHED Reserved 2026-03-23 | Published 2026-05-22 | Updated 2026-05-22 | Assigner Mattermost




MEDIUM: 6.5CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Problem types

CWE-362: Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')

Product status

Default status
unaffected

11.6.0 (semver)
affected

11.5.0 (semver)
affected

11.4.0 (semver)
affected

10.11.0 (semver)
affected

11.7.0
unaffected

11.6.1
unaffected

11.5.4
unaffected

11.4.5
unaffected

10.11.15
unaffected

Credits

daw10 finder

References

mattermost.com/security-updates (MMSA-2026-00637) vendor-advisory

cve.org (CVE-2026-4635)

nvd.nist.gov (CVE-2026-4635)

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