Vulnerability · Published Mar 16, 2026 · Assigned by Mattermost
CVE-2026-2456Denial of Service via Unbounded Memory Allocation in Integration Actions
Medium 5.3
In plain English
A medium-severity security flaw in Mattermost from Mattermost. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 7% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
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
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Go | github.com/mattermost/mattermost-server | 11.2.3 | GHSA-34g8-9fpp-46ch |
| Go | github.com/mattermost/mattermost-server | 5.3.2-0.20260127165411-fe3052073dc6 | GHSA-34g8-9fpp-46ch |
| Go | github.com/mattermost/mattermost-server | 10.11.11 | GHSA-34g8-9fpp-46ch |
| Go | github.com/mattermost/mattermost-server | 11.3.1 | GHSA-34g8-9fpp-46ch |
| Go | github.com/mattermost/mattermost-server | 10.11.11+incompatible, 11.2.3+incompatible, 11.3.1+incompatible | GO-2026-4726 |
| Go | github.com/mattermost/mattermost-server/v5 | no fix listed | GO-2026-4726 |
| Go | github.com/mattermost/mattermost-server/v6 | no fix listed | GO-2026-4726 |
| Go | github.com/mattermost/mattermost/server/v8 | 8.0.0-20260127165411-fe3052073dc6 | GO-2026-4726 |
| Go | github.com/mattermost/mattermost/server/v8 | 8.0.0-20260127165411-fe3052073dc6 | GHSA-34g8-9fpp-46ch |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| Mattermost | Mattermost | 11.3.0 – through 11.3.011.2.0 – through 11.2.210.11.0 – through 10.11.10 |
Weakness: CWE-789 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:N/A:H
References
- MMSA-2026-00571 vendor-advisory