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CVE-2026-4339

—
CVSS 3.1
6.5 medium
EPSS
<1%p4
Published
()
Modified
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

Vendors
mattermost
Products
mattermost server
Weakness
CWE-918
Vector
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N
NVD CVE.org GitHub PoCs EPSS (0.1%)

In the news

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