Request Size Validation Flaw in Mattermost Plugins Causes DoS

Publication date: 2026-03-26

Last updated on: 2026-06-08

Assigner: Mattermost, Inc.

Description

Mattermost Plugins versions <=11.4 11.0.4 11.1.3 11.3.2 10.11.11.0 fail to validate incoming request size which allows an authenticated attacker to cause service disruption via the webhook endpoint. Mattermost Advisory ID: MMSA-2026-00589

CVSS Scores

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Meta Information

Published

2026-03-26

Last Modified

2026-06-08

Generated

2026-07-06

AI Q&A

2026-03-26

EPSS Evaluated

2026-07-05

NVD

CVE-2026-3116

EUVD

EUVD-2026-16246

Affected Vendors & Products

Vendor	Product	Version / Range
mattermost	mattermost_server	From 10.11.0 (inc) to 10.11.12 (exc)
mattermost	mattermost_server	From 11.2.0 (inc) to 11.2.4 (exc)
mattermost	mattermost_server	From 11.3.0 (inc) to 11.3.2 (exc)
mattermost	mattermost_server	From 11.4.0 (inc) to 11.4.1 (exc)

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-400	The product does not properly control the allocation and maintenance of a limited resource.

Attack-Flow Graph

Executive Summary

This vulnerability exists in Mattermost Plugins versions up to 11.4, 11.0.4, 11.1.3, 11.3.2, and 10.11.11.0. The issue is that these versions fail to validate the size of incoming requests properly. Because of this, an authenticated attacker can exploit the webhook endpoint by sending oversized requests, which can disrupt the service.

Impact Analysis

The impact of this vulnerability is a potential service disruption. An authenticated attacker can cause denial of service by exploiting the webhook endpoint with oversized requests, leading to unavailability or degraded performance of the affected Mattermost Plugins.

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