What is CVE-2026-6333?

CVE-2026-6333 is a low-severity vulnerability in Mattermost, classified under Server-Side Request Forgery (SSRF). CVSS score: 3.5/10. Published 2026-05-18.

How severe is CVE-2026-6333?

Low severity. CVSS v3 base score is 3.5 out of 10.

SSRF in Mattermost

CVE-2026-6333

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-…

Vulnerability class: SSRF (Server-Side Request Forgery)

EPSS: 0.000 (9.4th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 3.5 (Low). Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:N/I:L/A:N.

Affected products

Mattermost — versions 11.5.0, 10.11.0, 11.6.0
Mattermost Mattermost_server

Weakness classification (CWE)

CWE-918 — Server-Side Request Forgery (SSRF)

References

responsibledisclosure@mattermost.com (vendor-advisory, Vendor Advisory)

Frequently asked questions

What is CVE-2026-6333?: CVE-2026-6333 is a low-severity vulnerability in Mattermost, classified under Server-Side Request Forgery (SSRF). CVSS score: 3.5/10. Published 2026-05-18.
How severe is CVE-2026-6333?: Low severity. CVSS v3 base score is 3.5 out of 10.