CVE-2026-4858

critical

Published 2026-05-21 · Modified 2026-05-21

CVSS v3

9.9

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

CVSS v2

—

VIR risk

9.9

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

Predictions

Exploit likelihood

98%

Patch ETA

—

Heuristic predictions, AS-IS, for prioritization only.

Mitigations

vendor Authored 2026-05-27

Vendor advisory: responsibledisclosure@mattermost.com — https://mattermost.com/security-updates

Application impact

Vendor	Product	Versions	Fixed
mattermost	mattermost_server	`{"startIncluding":"10.11.0","endExcluding":"10.11.15"}`	`10.11.15`
mattermost	mattermost_server	`11.6.0`

References

https://mattermost.com/security-updates

CWEs

CWE-22

Verify integrity in audit chain (admin only). AS-IS.