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9.9
CVE-2026-4858: Mattermost: Malicious Auth Token Exposure
CVE-2026-4858
Summary
Mattermost versions 11.6.x, 11.5.x, and 10.11.x are vulnerable to a security issue that allows an authenticated user to access sensitive information. This issue affects users who have system admin privileges. To protect your Mattermost instance, update to a patched version.
What to do
No fix is available yet. Check with your software vendor for updates.
Affected software
| Vendor | Product | Affected versions |
|---|---|---|
| mattermost | mattermost_server |
>= 10.11.0, < 10.11.15 >= 11.4.0, < 11.4.5 >= 11.5.0, < 11.5.4 11.6.0 cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:* |
Original title
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 ...
Original 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
nvd CVSS3.1
8.0
Vulnerability type
CWE-22
Path Traversal
Published: 21 May 2026 · Updated: 28 May 2026 · First seen: 21 May 2026