CVE-2026-21388

Received Received - Intake

Denial of Service via Memory Exhaustion in Mattermost Plugins

Publication date: 2026-04-09

Last updated on: 2026-04-25

Assigner: Mattermost, Inc.

Description

Mattermost Plugins versions <=2.3.1 fail to limit the request body size on the {{/lifecycle}} webhook endpoint which allows an authenticated attacker to cause memory exhaustion and denial of service via sending an oversized JSON payload. Mattermost Advisory ID: MMSA-2026-00610

CVSS Scores

EPSS Scores

Probability:
Percentile:

Meta Information

Published

2026-04-09

Last Modified

2026-04-25

Generated

2026-07-26

AI Q&A

2026-04-09

EPSS Evaluated

2026-07-25

NVD

CVE-2026-21388

EUVD

EUVD-2026-20880

Affected Vendors & Products

Vendor	Product	Version / Range
mattermost	mattermost_server	to 2.3.1 (inc)

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-770	The product allocates a reusable resource or group of resources on behalf of an actor without imposing any intended restrictions on the size or number of resources that can be allocated.

Attack-Flow Graph

Executive Summary

Mattermost Plugins versions up to 2.3.1 have a vulnerability where the request body size is not limited on the {{/lifecycle}} webhook endpoint.

This allows an authenticated attacker to send an oversized JSON payload which can cause memory exhaustion and lead to a denial of service.

Impact Analysis

The vulnerability can be exploited by an authenticated attacker to cause memory exhaustion on the affected system.

This results in a denial of service condition, potentially making the Mattermost Plugins unavailable or unstable.

Hi! I’m here to help you understand CVE-2026-21388. Ask me anything about the vulnerability, its impact, or mitigation strategies.

0/70