CVE-2026-6334: Mattermost doesn't enforce client identity binding during the OAuth authorization code redemption flow

May 18, 2026 (updated June 1, 2026)

Mattermost versions 11.5.x <= 11.5.1, 10.11.x <= 10.11.13 fail to enforce client identity binding during the OAuth authorization code redemption flow which allows an authenticated OAuth client to redeem authorization codes issued to a different client via a crafted token exchange request.. Mattermost Advisory ID: MMSA-2026-00570

References

github.com/advisories/GHSA-jp3f-x449-4q75
github.com/mattermost/mattermost/commit/e9ae890a013bb57989fcbdb548d8b7b86b240237
mattermost.com/security-updates
nvd.nist.gov/vuln/detail/CVE-2026-6334

Code Behaviors & Features

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