PT-2026-31603 · Mattermost · Mattermost Plugins

Lorenzo Gallegos · Published 2026-04-09 · Updated 2026-04-10 · CVE-2026-21388

Positive Technologies (AI Summary)

CVSS v3.1

6.5

Medium

Base vector

AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Name of the Vulnerable Software and Affected Versions Mattermost Plugins versions less than or equal to 2.3.1

Description Mattermost Plugins versions less than or equal to 2.3.1 do not limit the request body size on the /lifecycle webhook endpoint, potentially allowing an authenticated attacker to cause memory exhaustion and denial of service by sending an oversized JSON payload.

Recommendations Update Mattermost Plugins to a version greater than 2.3.1.

Fix

Allocation of Resources Without Limits

Weakness Enumeration

CWE-770

Related Identifiers

CVE-2026-21388

GHSA-X274-8QFC-HRGF

Affected Products

Mattermost Plugins

References · 7

• https://osv.dev/vulnerability/GHSA-x274-8qfc-hrgf · Vendor Advisory
• https://nvd.nist.gov/vuln/detail/CVE-2026-21388 · Security Note
• https://mattermost.com/security-updates · Vendor Advisory
• https://github.com/mattermost/mattermost-plugin-msteams · Note
• https://github.com/mattermost/mattermost-plugin-msteams/commit/6fe4d295592ecc8767d67e69286cbeec01be3210 · Note
• https://github.com/mattermost/mattermost-plugin-msteams/releases/tag/v2.3.2 · Note
• https://twitter.com/CVEarity/status/2042585507570598318 · Twitter Post