What is CVE-2026-2456?

CVE-2026-2456 is a medium-severity vulnerability in Mattermost, classified under CWE-789. CVSS score: 5.3/10. Published 2026-03-16.

How severe is CVE-2026-2456?

Medium severity. CVSS v3 base score is 5.3 out of 10.

Vulnerability in Mattermost

CVE-2026-2456

Mattermost versions 11.3.x <= 11.3.0, 11.2.x <= 11.2.2, 10.11.x <= 10.11.10 Mattermost fails to limit the size of responses from integration action endpoints, which allows an authenticated attacker to cause server memory exhaustion and denial of service via a malicious integration server that returns an arbitrarily large response when a user clicks an interactive message button.. Mattermost Advisory ID: MMSA-2026-00571

EPSS: 0.002 (6.1th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 5.3 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:N/A:H.

Affected products

Mattermost — versions 11.3.0, 11.2.0, 10.11.0
Mattermost Mattermost_server

Weakness classification (CWE)

CWE-789

References

responsibledisclosure@mattermost.com (vendor-advisory, Vendor Advisory)

Frequently asked questions

What is CVE-2026-2456?: CVE-2026-2456 is a medium-severity vulnerability in Mattermost, classified under CWE-789. CVSS score: 5.3/10. Published 2026-03-16.
How severe is CVE-2026-2456?: Medium severity. CVSS v3 base score is 5.3 out of 10.