CVE-2026-16453 json
Mattermost SAML RelayState forgery allows unauthorized team membership
published 2026-10-16 24 d ago modified 2026-10-29 10 d ago also EUVD-2026-102745
- cvss
- 7.1
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.2%
- EPSS 0.2% chance of exploitation in 30 days, percentile 8%
- public exploits
- 0
- none known
Summary
Mattermost versions 11.10.x <= 11.10.0, 11.7.x <= 11.7.9, 11.9.x <= 11.9.1, 11.8.x <= 11.8.5 fail to verify the integrity of the SAML RelayState POST parameter which allows an authenticated SAML user to join any team, including invite-only teams, via forging the team_id or invite_id fields in the RelayState.. Mattermost Advisory ID: MMSA-2026-00727
Patch / fix
- Mattermost Mattermost 11.7.10, 11.8.6, 11.9.2, 11.10.1, 11.11.0
CISA SSVC
- Exploitation
- none
- Automatable
- no
- Technical impact
- partial
- Assessed
- 24 d ago
Exploit prediction
0.19% chance of exploitation in the next 30 days, higher than 8% of all scored CVEs (FIRST EPSS, 2026-11-08).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 3.1 | 7.1 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:N |
Affected products
- Mattermost Mattermost
Classification
- Weakness
-
- CWE-472 External Control of Assumed-Immutable Web Parameter
References
-
mattermost.com
/security-updates
vendor-advisory
Sources
- CVE List CVE-2026-16453
- NVD CVE-2026-16453
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