What is GHSA-p3qg-h7r3-79xr?

GHSA-p3qg-h7r3-79xr is a security advisory published by GitHub Security Advisories with Medium severity. Mattermost versions 10.11.x \u003c= 10.11.18, 11.6.x \u003c= 11.6.3, 11.5.x \u003c= 11.5.6 fail to validate...

Which CVE IDs does GHSA-p3qg-h7r3-79xr cover?

GHSA-p3qg-h7r3-79xr covers the following CVE IDs: CVE-2026-4339. Each CVE has its own detail page on EchelonGraph Pulse with the synthesized EG score.

What is the CVSS v3 score of GHSA-p3qg-h7r3-79xr?

GHSA-p3qg-h7r3-79xr has a CVSS v3 base score of 6.5, published by GitHub Security Advisories.

GHSA-p3qg-h7r3-79xrMediumCVSS 6.5

Mattermost versions 10.11.x <= 10.11.18, 11.6.x <= 11.6.3, 11.5.x <= 11.5.6 fail to validate...

Vendor

GitHub Security Advisories

Published

June 26, 2026

Last Modified

June 26, 2026

🔗 CVE IDs covered (1)

CVE-2026-4339 →

📋 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

🔗 References (3)

https://nvd.nist.gov/vuln/detail/CVE-2026-4339
https://mattermost.com/security-updates
https://github.com/advisories/GHSA-p3qg-h7r3-79xr