Channel Archiving Flaw in Mattermost Affects Multiple Versions
CVE-2026-4635

6.5MEDIUM

Key Information:

Vendor

Mattermost
Status
Mattermost
Vendor
CVE Published:
22 May 2026

What is CVE-2026-4635?

A flaw in Mattermost allows authenticated users to potentially crash the server due to improper handling of persistent notifications before channel archiving. This occurs when a user creates a persistent notification message at a specific time, leading to a race condition as the server attempts to delete existing notifications and archive the channel. This can disrupt service availability in the affected Mattermost versions.

Affected Version(s)

Mattermost 11.6.0

Mattermost 11.5.0 <= 11.5.3

Mattermost 11.4.0 <= 11.4.4

References

https://mattermost.com/security-updates
vendor-advisory

CVSS V3.1

Score:
6.5
Severity:
MEDIUM
Confidentiality:
None
Integrity:
None
Availability:
None
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
Low
User Interaction:
None
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

Credit

daw10
.