CVE-2026-27826

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.

• CWE-918

• https://github.com/sooperset/mcp-atlassian/commit/5cd697dfce9116ef330b8dc7a91291640e0528d9Patch
• https://github.com/sooperset/mcp-atlassian/security/advisories/GHSA-7r34-79r5-rcc9Exploit, Vendor Advisory

Published

Mar 10, 2026

Last Modified

Jun 17, 2026

Status

Analyzed

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