PT-2026-52722 · Mattermost · Mattermost
S00Me00Ne
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Published
2026-06-26
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Updated
2026-06-26
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CVE-2026-4339
CVSS v3.1
6.5
Medium
| Vector | AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N |
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
Fix
SSRF
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Weakness Enumeration
Related Identifiers
Affected Products
Mattermost