CVE-2026-4646: Mattermost doesn't validate user-supplied input in API request handlers

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 validate user-supplied input in API request handlers which allows an authenticated attacker to crash the plugin process via a crafted HTTP request to the PR details endpoint. Mattermost Advisory ID: MMSA-2026-00638

References

github.com/advisories/GHSA-rmvv-8v8w-rf7x
github.com/mattermost/mattermost-plugin-github/commit/c2840e980b3c2bd08db656eaa6a0fe26bcbf4695
mattermost.com/security-updates
nvd.nist.gov/vuln/detail/CVE-2026-4646

Code Behaviors & Features

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