CVE-2026-4858

Name: CVE-2026-4858
Creator: NVD / NIST
Published: 2026-05-21T09:16:30.143+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

CRITICALCVSS 9.9/10EPSS 0.25%

Last modified Jun 17, 2026

CVE-2026-4858 is a critical-severity vulnerability rated 9.9/10 on the CVSS scale. 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 Mattermost auth token using via path traversal in integration action URL.. Mattermost Advisory ID: MMSA-2026-00640. EPSS estimates a 0.25% chance of exploitation in the next 30 days.

Description

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 Mattermost auth token using via path traversal in integration action URL.. Mattermost Advisory ID: MMSA-2026-00640

Metrics

CVSS 3.1

9.9/10

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

EPSS Probability

0.25%

16.1th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-22

Affected Software

Vendor	Product	Versions
Mattermost	Mattermost Server	>= 10.11.0, < 10.11.15
Mattermost	Mattermost Server	>= 11.4.0, < 11.4.5
Mattermost	Mattermost Server	>= 11.5.0, < 11.5.4
Mattermost	Mattermost Server	11.6.0

References

https://mattermost.com/security-updatesVendor Advisory

Timeline

Published: May 21, 2026
Last Modified: Jun 17, 2026
Status: Analyzed

Frequently Asked Questions

What is CVE-2026-4858?

How severe is CVE-2026-4858?

CVE-2026-4858 has a CVSS score of 9.9/10 (CRITICAL severity). The EPSS model estimates a 0.25% probability of exploitation in the next 30 days.

How do I fix CVE-2026-4858?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2026-4858?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST