CVE-2026-26233

EUVD-2026-15756
Mattermost versions 11.4.x <= 11.4.0, 11.3.x <= 11.3.1, 11.2.x <= 11.2.3, 10.11.x <= 10.11.11 fail to rate limit login requests which allows unauthenticated remote attackers to cause denial of service (server crash and restart) via HTTP/2 single packet attack with 100+ parallel login requests.. Mattermost Advisory ID: MMSA-2025-00566
ProviderTypeBase ScoreAtk. VectorAtk. ComplexityPriv. RequiredVector
MattermostCNA
4.3 MEDIUM
NETWORK
LOW
LOW
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L
Base Score
CVSS 3.x
EPSS Score
Percentile: 28%
Affected Products (NVD)
VendorProductVersion
mattermostmattermost_server
10.11.0 ≤
𝑥
< 10.11.12
mattermostmattermost_server
11.2.0 ≤
𝑥
< 11.2.4
mattermostmattermost_server
11.3.0 ≤
𝑥
< 11.3.2
mattermostmattermost_server
11.4.0 ≤
𝑥
< 11.4.1
𝑥
= Vulnerable software versions
Early Detection
Affected products identified ahead of NVD analysis through intelligence sources.
VendorProductVersionSource
mattermostmattermost
𝑥
≤ 11.4.0
CNA
mattermostmattermost
11.3.0 ≤
𝑥
≤ 11.3.1
CNA
mattermostmattermost
11.2.0 ≤
𝑥
≤ 11.2.3
CNA
mattermostmattermost
10.11.0 ≤
𝑥
≤ 10.11.11
CNA
Common Weakness Enumeration
References
https://mattermost.com/security-updates