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CVE-2026-4635

Persistent notification timing attack causing server denial of service

Published: May 22, 2026Updated: May 22, 2026 Sources: CVE List BDUCWE-362CWE-362: Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')
NVD MITRE
6.5CVSSMEDIUM
EPSS Score
0.2%
Top 93.2%
CISA KEV
Not in KEV
Exploits
No Known Exploits
Remediation
Patch Available

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

CVSS Vector Breakdown

AV:NAC:LPR:LUI:NS:UC:NI:NA:H
Exploitability
AV:NAttack Vector
Network
AC:LAttack Complexity
Low
PR:LPrivileges Required
Low
UI:NUser Interaction
None
Scope
S:UScope
Unchanged
Impact
C:NConfidentiality
None
I:NIntegrity
None
A:HAvailability
High
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Weaknesses

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

Affected Products

MattermostMattermost Inc
On-premWeb App
Communications / messaging-chat
MattermostMattermost
On-premWeb App
Communications / messaging-chat
mattermost inccommercialUSCommunicationsaka mattermost
mattermostcommercialUSCommunications

Attack Graph

Products CVE Techniques Tactics

Click technique nodes to view MITRE ATT&CK details. Scroll to zoom, drag to pan.

Exploitability

Official Patch Available

MITRE ATT&CK

1 technique
Privilege Escalation
View detailed technique mapping

References

https://mattermost.com/security-updates&#13;
mattermost.com
https://vuldb.com/vuln/365182
vuldb.com
https://mattermost.com/security-updates
mattermost.com

Timeline

Published
May 22, 2026
Last Updated
May 22, 2026

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