CVE-2026-5308: Mattermost doesn't enforce request body size limits on plugin HTTP endpoints

May 26, 2026 (updated June 29, 2026)

Mattermost versions 11.6.x <= 11.6.0, 11.5.x <= 11.5.3, 11.4.x <= 11.4.4, 10.11.x <= 10.11.14 fail to enforce request body size limits on plugin HTTP endpoints which allows an attacker to cause a denial of service via crafted oversized HTTP requests.. Mattermost Advisory ID: MMSA-2026-00646

References

github.com/advisories/GHSA-jmvr-r5hm-fxfr
github.com/mattermost/mattermost-plugin-github/commit/9b41b1fd43c408f4be53026ee337bbeaa74ad47c
mattermost.com/security-updates
nvd.nist.gov/vuln/detail/CVE-2026-5308

Code Behaviors & Features

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