CVE-2026-6334

OAuth authorization code client binding not enforced during token redemption in Mattermost

State: Published
Severity: 3.1 Low
Published: May 18, 2026
Updated: May 18, 2026
Reserved: Apr 15, 2026

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

Scores

CVSS	Score	Vector	Source
3.1	3.1 Low	CVSS:3.1/AV:N/AC:H/PR:H/UI:R/S:U/C:L/I:L/A:N	Mattermost

Weaknesses

CWE-305 – Authentication Bypass by Primary Weakness

Affected Products

Product	Versions
MattermostMattermost	11.5.0 through 11.5.1Affected 10.11.0 through 10.11.13Affected 11.6.0Not affected 11.5.2Not affected 10.11.14Not affected

References

MMSA-2026-00570vendor-advisory

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