Low 3.1Published May 18, 2026

CVE-2026-6334OAuth authorization code client binding not enforced during token redemption in Mattermost

Updated under an hour ago (Oct 26, 2026, 4:40 PM ET)

Does this affect you?

It affects Mattermost and 1 other product. Add what you run to find out whether that includes you.

No exploitation reported and no EPSS estimate yet.

Do this next

Start free and add your stack

Free account, 1 product

Every CVE for Mattermost

Exploited in the last 30 days

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 LOW (v3.1, CNA)CVSS:3.1/AV:N/AC:H/PR:H/UI:R/S:U/C:L/I:L/A:N
Weakness (CWE): CWE-305
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: Mattermost
NVD analysis: Analyzed
Record last updated: May 18, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

Mattermost Mattermost mattermost:mattermost (from the name)	from 11.5.0 through 11.5.1; from 10.11.0 through 10.11.13; 11.6.0 not affected; 11.5.2 not affected; 10.11.14 not affected	CNA record
mattermost mattermost_server mattermost:mattermost_server	from 10.11.0 before 10.11.14; from 11.5.0 before 11.5.2	NVD

References

References

https://mattermost.com/security-updates	vendor-advisory

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.