CVE-2026-28735

EUVD-2026-31465
Mattermost versions 11.6.x <= 11.6.0, 11.5.x <= 11.5.3, 11.4.x <= 11.4.4, 10.11.x <= 10.11.14 fail to validate the OAuth token scope on the callback which allows an authenticated Mattermost user to gain access to private repositories via modifying the scope parameter in the GitHub authorization URL.. Mattermost Advisory ID: MMSA-2026-00628
ProviderTypeBase ScoreAtk. VectorAtk. ComplexityPriv. RequiredVector
MattermostCNA
5.4 MEDIUM
NETWORK
LOW
LOW
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N
Base Score
CVSS 3.x
EPSS Score
Percentile: 3%
Affected Products (NVD)
VendorProductVersion
mattermostmattermost_server
10.11.0 ≤
𝑥
< 10.11.15
mattermostmattermost_server
11.4.0 ≤
𝑥
< 11.4.5
mattermostmattermost_server
11.5.0 ≤
𝑥
< 11.5.4
mattermostmattermost_server
11.6.0 ≤
𝑥
< 11.6.1
𝑥
= Vulnerable software versions
Early Detection
Affected products identified ahead of NVD analysis through intelligence sources.
VendorProductVersionSource
mattermostmattermost
𝑥
≤ 11.6.0
CNA
mattermostmattermost
11.5.0 ≤
𝑥
≤ 11.5.3
CNA
mattermostmattermost
11.4.0 ≤
𝑥
≤ 11.4.4
CNA
mattermostmattermost
10.11.0 ≤
𝑥
≤ 10.11.14
CNA