Mattermost versions 11.5.x <= 11.5.1, 10.11.x <= 10.11.13 fail to validate the Host header when constructing response URLs for custom slash commands which allows an authenticated attacker to redirect slash command responses to an attacker-controlled server via a spoofed Host header.. Mattermost Advisory ID: MMSA-2026-00582
References
History

Tue, 19 May 2026 18:15:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Tue, 19 May 2026 18:00:00 +0000

Type Values Removed Values Added
First Time appeared Mattermost mattermost Server
CPEs cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*
Vendors & Products Mattermost mattermost Server

Mon, 18 May 2026 10:45:00 +0000

Type Values Removed Values Added
First Time appeared Mattermost
Mattermost mattermost
Vendors & Products Mattermost
Mattermost mattermost

Mon, 18 May 2026 09:00:00 +0000

Type Values Removed Values Added
Description Mattermost versions 11.5.x <= 11.5.1, 10.11.x <= 10.11.13 fail to validate the Host header when constructing response URLs for custom slash commands which allows an authenticated attacker to redirect slash command responses to an attacker-controlled server via a spoofed Host header.. Mattermost Advisory ID: MMSA-2026-00582
Title SSRF via Host Header Spoofing in Custom Slash Commands
Weaknesses CWE-918
References
Metrics cvssV3_1

{'score': 3.5, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:N/I:L/A:N'}


cve-icon MITRE

Status: PUBLISHED

Assigner: Mattermost

Published: 2026-05-18T08:41:29.342Z

Updated: 2026-05-19T17:19:42.466Z

Reserved: 2026-04-15T08:51:33.309Z

Link: CVE-2026-6333

cve-icon Vulnrichment

Updated: 2026-05-18T14:36:17.582Z

cve-icon NVD

Status : Analyzed

Published: 2026-05-18T09:16:23.430

Modified: 2026-05-19T17:51:43.453

Link: CVE-2026-6333

cve-icon Redhat

No data.