What is CVE-2026-4858?

CVE-2026-4858 is a high-severity vulnerability in Mattermost, classified under Path Traversal. CVSS score: 8.0/10. Published 2026-05-21.

How severe is CVE-2026-4858?

High severity. CVSS v3 base score is 8.0 out of 10.

Path Traversal in Mattermost

CVE-2026-4858

Mattermost versions 11.6.x <= 11.6.0, 11.5.x <= 11.5.3, 11.4.x <= 11.4.4, 10.11.x <= 10.11.14 fail to check integration URL for path traversal which allows an malicious authenticated user to call an arbitrary API via system admin Mattermo…

Vulnerability class: Path Traversal (Directory Traversal)

EPSS: 0.000 (14.4th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 8.0 (High). Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:H/I:H/A:H.

Affected products

Mattermost — versions 11.6.0, 11.5.0, 11.4.0
Mattermost Mattermost_server — versions 11.6.0

Weakness classification (CWE)

CWE-22 — Path Traversal

References

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

Frequently asked questions

What is CVE-2026-4858?: CVE-2026-4858 is a high-severity vulnerability in Mattermost, classified under Path Traversal. CVSS score: 8.0/10. Published 2026-05-21.
How severe is CVE-2026-4858?: High severity. CVSS v3 base score is 8.0 out of 10.