CVE-2026-95666

Mattermost versions 11.9.x <= 11.9.1, 11.8.x <= 11.8.5, 11.7.x <= 11.7.10, 11.10.x <= 11.10.1 fail to limit the length of the post ID array accepted by the bulk reactions endpoint which allows an authenticated user to cause excessive database load via a crafted request to {{POST /api/v4/posts/ids/reactions}}.. Mattermost Advisory ID: MMSA-2026-00771

CVSS v3 4.3 MEDIUM

4.3^/10

CVSS v3 : MEDIUM

Vector :

Exploitability : 2.8 / Impact : 1.4

Attack Vector NETWORK

Attack Complexity LOW

Privileges Required LOW

User Interaction NONE

Confidentiality Impact NONE

Integrity Impact NONE

Availability Impact LOW

Scope UNCHANGED

References

Link	Resource
https://mattermost.com/security-updates	Vendor Advisory

Configurations

Configuration 1 (hide)

OR	cpe:2.3:a:mattermost:mattermost_server::::::::
	cpe:2.3:a:mattermost:mattermost_server::::::::
	cpe:2.3:a:mattermost:mattermost_server::::::::
	cpe:2.3:a:mattermost:mattermost_server::::::::

History

07 Oct 2026, 16:48

Type	Values Removed	Values Added
First Time		Mattermost mattermost Server Mattermost
CPE		cpe:2.3:a:mattermost:mattermost_server::::::::
References	~~() https://mattermost.com/security-updates -~~	() https://mattermost.com/security-updates - Vendor Advisory

22 Sep 2026, 14:17

Type	Values Removed	Values Added
New CVE

Information

Published : 2026-09-22 14:17

Updated : 2026-10-07 16:48

NVD link : CVE-2026-95666

Mitre link : CVE-2026-95666

CVE.ORG link : CVE-2026-95666

JSON object : View

Products Affected

mattermost

mattermost_server

CWE

CWE-770

Allocation of Resources Without Limits or Throttling

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