MCP Atlassian — Vulnerability (CVE-2026-27826)
Date: 2026-03
Affected: sooperset/mcp_atlassian
Attack vector: ssrf
Category: vulnerability-disclosure
Severity: High
CVE: CVE-2026-27826
CWE: CWE-918
CVSS: 8.2 (CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:H/I:L/A:N)

MCP Atlassian is a Model Context Protocol (MCP) server for Atlassian products (Confluence and Jira). Prior to version 0.17.0, an unauthenticated attacker who can reach the mcp-atlassian HTTP endpoint can force the server process to make outbound HTTP requests to an arbitrary attacker-controlled URL by supplying two custom HTTP headers without an `Authorization` header. No authentication is required. The vulnerability exists in the HTTP middleware and dependency injection layer — not in any MCP tool handler - making it invisible to tool-level code analysis. In cloud deployments, this could enable theft of IAM role credentials via the instance metadata endpoint (`169[.]254[.]169[.]254`). In any HTTP deployment it enables internal network reconnaissance and injection of attacker-controlled content into LLM tool results. Version 0.17.0 fixes the issue.


Mitigations:

Architectural layers (MAESTRO):