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Description

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

PUBLISHED Reserved 2026-04-15 | Published 2026-05-18 | Updated 2026-05-18 | Assigner Mattermost




LOW: 3.1CVSS:3.1/AV:N/AC:H/PR:H/UI:R/S:U/C:L/I:L/A:N

Problem types

CWE-305 – Authentication Bypass by Primary Weakness

Product status

Default status
unaffected

11.5.0 (semver)
affected

10.11.0 (semver)
affected

11.6.0
unaffected

11.5.2
unaffected

10.11.14
unaffected

Credits

Dylan Haussermann finder

References

mattermost.com/security-updates (MMSA-2026-00570) vendor-advisory

cve.org (CVE-2026-6334)

nvd.nist.gov (CVE-2026-6334)

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