← Back

CVE-2026-4339

nvd nist
Published: Jun 26, 2026Modified: Jun 29, 2026

JSON object

Loading...
6.5
Vector
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N
Exploitability: 2.0 / Impact: 4.0
Source: responsibledisclosure@mattermost.com (Secondary)

Description

Mattermost versions 10.11.x <= 10.11.18, 11.6.x <= 11.6.3, 11.5.x <= 11.5.6 fail to validate attachment URLs against internal or private IP ranges in the Mattermost Agents plugin MCP server which allows an attacker with access to the MCP server in stdio mode to perform server-side request forgery (SSRF) and exfiltrate data from internal network services via supplying internal URLs as file attachments in post creation requests.. Mattermost Advisory ID: MMSA-2026-00635

Affected (3)

Mattermost
1 product
Mattermost Server
Configuration A
3 vulnerable
Vulnerable SoftwareAffected Versions
Mattermost
Mattermost Server
From 10.11.0 to 10.11.19
Mattermost Server
From 11.5.0 to 11.5.7
Mattermost Server
From 11.6.0 to 11.6.4

Related CWEs

CWE-918
Server-Side Request Forgery (SSRF)
The web server receives a URL or similar request from an upstream component and retrieves the contents of this URL, but it does not sufficiently ensure that the request is being sent to the expected destination.

References (1)

Source: responsibledisclosure@mattermost.com
Vendor Advisory

Timeline

No history available yet.