CVE-2026-4339

The record

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 packages

Related vulnerabilities

• CVE-2026-114730 Roundcube Webmail 1.6.14 before 1.6.20 and 1.7.0 before 1.7.5 is affected by a… CWE-918
• CVE-2026-87953 Server-Side Request Forgery (SSRF) vulnerability in Drupal SAML SSO - Service Provider… CWE-918
• CVE-2026-114634 WWBN AVideo before 29.4.0 contains a blind server-side request forgery vulnerability in… CWE-918
• CVE-2026-112288 Krayin CRM 2.2.5 before 2.2.7 contains a server-side request forgery filter bypass that… CWE-918
• CVE-2026-111936 Sigma File Manager through 2.2.0 contains a server-side request forgery vulnerability… CWE-918
• CVE-2026-94483 Next.js is a React framework for building full-stack web applications. CWE-918
• CVE-2026-102267 PyJWT is a Python implementation of JSON Web Token standards. CWE-918
• CVE-2026-101913 ip-address is a library for parsing and manipulating IPv4 and IPv6 addresses in… CWE-918