CVE-2026-21388: 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…

PriorityP434medium6.5CVSS 3.1

AVNACLPRLUINSUCNINAH

EPSS

0.31%

23.4th percentile

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

Affected

3 ranges

Vendor	Product	Version range	Fixed in
github.com	mattermost_mattermost-plugin-msteams	>= 0 < 1.15.1-0.20260213190728-6fe4d295592e	1.15.1-0.20260213190728-6fe4d295592e
mattermost	mattermost	<= 2.3.1	—
mattermost	mattermost_server	<= 2.3.1	—

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