CVE-2026-6333 LOW

CVE-2026-6333: SSRF via Host Header Spoofing in Custom Slash Commands

Vendor Mattermost
Product Mattermost
Weakness CWE-918 · SSRF
Published May 18, 2026
Last update May 19, 2026
View on NVD All CVEs

CVSS base score

3.5/10
Attack vector Network
Attack complexity High
Privileges required Low
User interaction None
Confidentiality None
Integrity Low

CVSS vector

CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:N/I:L/A:N

What the vulnerability does

01Description

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

Key dates

02Disclosure timeline

May 18, 2026 CVE published
May 19, 2026 Record updated