CVE-2026-2456
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Denial of Service via Memory Exhaustion in Mattermost Integrations

Publication date: 2026-03-16

Last updated on: 2026-03-18

Assigner: Mattermost, Inc.

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

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Meta Information

Published
2026-03-16
Last Modified
2026-03-18
Generated
2026-07-06
AI Q&A
2026-03-16
EPSS Evaluated
2026-07-05
NVD
CVE-2026-2456
EUVD
EUVD-2026-12383

Affected Vendors & Products

Showing 3 associated CPEs
Vendor Product Version / Range
mattermost mattermost_server From 10.11.0 (inc) to 10.11.11 (exc)
mattermost mattermost_server From 11.2.0 (inc) to 11.2.3 (exc)
mattermost mattermost_server From 11.3.0 (inc) to 11.3.1 (exc)

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Exploitability

CWE
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KEV
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CWE ID Description
CWE-789 The product allocates memory based on an untrusted, large size value, but it does not ensure that the size is within expected limits, allowing arbitrary amounts of memory to be allocated.

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Executive Summary

This vulnerability exists in Mattermost versions 11.3.x <= 11.3.0, 11.2.x <= 11.2.2, and 10.11.x <= 10.11.10. It occurs because Mattermost does not limit the size of responses from integration action endpoints.

An authenticated attacker can exploit this by using a malicious integration server that returns an arbitrarily large response when a user clicks an interactive message button.

This can cause the server to exhaust its memory, leading to a denial of service condition.

Impact Analysis

The primary impact of this vulnerability is a denial of service (DoS) on the Mattermost server.

An attacker who is authenticated can cause the server to consume excessive memory by sending large responses through a malicious integration, potentially making the service unavailable to legitimate users.

Compliance Impact

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