CVE-2026-16453CWE-472

CVE-2026-16453

High · published October 16, 2026

CVSS v3.1
7.1
EPSS
0%
Percentile
7.8
In the wild
Unconfirmed
What it is

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

The record
Technical detail
CVSS v3.1
7.1 · HIGH
Vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:N
CVSS v4.0
Not supplied
EPSS
0.00186 · 7.8th percentile
Weakness
CWE-472 · External Control of Assumed-Immutable Web Parameter
Published
2026-10-16T12:17Z
References (1)
https://mattermost.com/security-updates · [email protected]
EPSS history
Timeline
  • 17 OCT 03:28Z
    EPSS moved — → 0%
    epss
  • 16 OCT 07:08Z
    Mattermost SAML RelayState forgery allows unauthorized team membership
    cvelistv5
  • 16 OCT 07:08Z
    Mattermost SAML RelayState forgery allows unauthorized team membership
    cvelistv5