CVE-2026-15754CWE-863broken-access-control

CVE-2026-15754

Medium · published August 17, 2026

CVSS v3.1
4.2
EPSS
0%
Percentile
14.9
In the wild
Unconfirmed
What it is

Mattermost versions 11.7.x <= 11.7.6, 11.8.x <= 11.8.3 The access control policy unassign endpoint fails to re-validate that each target channel still belongs to the requesting admin's team, which allows an authenticated team administrator to remove ABAC (attribute-based access control) policy assignments from channels outside their team via the policy unassign API after a channel has been moved to another team.. Mattermost Advisory ID: MMSA-2026-00718

The record
Technical detail
CVSS v3.1
4.2 · MEDIUM
Vector
CVSS:3.1/AV:N/AC:H/PR:H/UI:R/S:U/C:N/I:H/A:N
CVSS v4.0
Not supplied
EPSS
0.00246 · 14.9th percentile
Weakness
CWE-863 · Incorrect Authorization
Published
2026-08-17T19:16Z
Affected products (2)
ProductVersionsFixed in
mattermost/mattermost_server≥ 11.7.0, < 11.7.711.7.7
mattermost/mattermost_server≥ 11.8.0, < 11.8.411.8.4
References (1)
https://mattermost.com/security-updates · [email protected]
EPSS history
Timeline
  • 17 AUG 14:36Z
    Missing per-channel team-scope check in ABAC access control policy unassign allows cross-team policy removal
    cvelistv5