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
Published: 2026-05-18
Score: 3.5 Low
EPSS: < 1% Very Low
KEV: No
Impact: n/a
Action: n/a
AI Analysis

Analysis and contextual insights are available on OpenCVE Cloud.

Remediation

Vendor Solution

Update Mattermost to versions 11.6.0, 11.5.2, 10.11.14 or higher.

Tracking

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Advisories
Source ID Title
Github GHSA Github GHSA GHSA-vqp5-2mrp-qqxg Mattermost doesn't validate the Host header when constructing response URLs for custom slash command
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'}


Subscriptions

Mattermost Mattermost Mattermost Server
cve-icon MITRE

Status: PUBLISHED

Assigner: Mattermost

Published:

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: 2026-06-17T11:00:40.673

Link: CVE-2026-6333

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-05-18T10:30:23Z

Weaknesses