CVE-2026-18223CWE-863broken-access-control

CVE-2026-18223

Medium · published October 16, 2026

CVSS v3.1
5.0
EPSS
0%
Percentile
4.9
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 validate the invited recipient's email address when redeeming team and guest invitation tokens, which allows an authenticated attacker to join a team or gain unauthorized access to private channels via a forwarded or leaked invitation link.. Mattermost Advisory ID: MMSA-2026-00747

The record
Technical detail
CVSS v3.1
5.0 · MEDIUM
Vector
CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:L/A:N
CVSS v4.0
Not supplied
EPSS
0.00161 · 4.9th percentile
Weakness
CWE-863 · Incorrect Authorization
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 07:12Z
    Mattermost invitation tokens not bound to invited email address allowing unauthorized team and private channel access
    cvelistv5
  • 16 OCT 07:12Z
    Mattermost invitation tokens not bound to invited email address allowing unauthorized team and private channel access
    cvelistv5