CVE-2026-21388
Mattermost MS Teams plugin doesn't limit the request body size on the /lifecycle webhook endpoint
3.7
LOW
CVSS 3.1
EPSS 0.02%
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.
How to fix CVE-2026-21388
To remediate CVE-2026-21388, upgrade the affected package to a fixed version below.
- —upgrade to 1.15.1-0.20260213190728-6fe4d295592e or later
Is CVE-2026-21388 being exploited?
Low — EPSS is 0.0%, meaning exploitation activity has not been observed at scale.
Affected packages (1)
- from 0, < 1.15.1-0.20260213190728-6fe4d295592e
CVSS scores
| Source | Version | Severity | Vector |
|---|---|---|---|
| osv | CVSS 3.1 | LOW3.7 | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L |