CVE-2026-6334

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

CVSS 3.1 LOWEPSS 0.1%CWE-305

Vexday Risk Score

8Low

SSVC decision (CISA)

Track

No exploitation signal → monitor

CVSS 3.1EPSS 0.1%KEV nãoPoC —Nuclei —Metasploit —Patch referenciado

Lifecycle

18 May 2026Published on NVD

Recommendation: Monitor — no exploitation signal at the moment.

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

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

Affected products

Mattermost · Mattermost

Want to know if your infrastructure is exposed to this?

Talk to TrueHacking →

References

https://mattermost.com/security-updates