CVE-2026-2456: Mattermost fails to limit the size of responses from integration action endpoints

March 16, 2026 (updated March 17, 2026)

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

References

github.com/advisories/GHSA-34g8-9fpp-46ch
github.com/mattermost/mattermost
github.com/mattermost/mattermost/commit/fe3052073dc67e3c920baf9fe7efd44ac1d8124c
mattermost.com/security-updates
nvd.nist.gov/vuln/detail/CVE-2026-2456

Code Behaviors & Features

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