Model Context Protocol Vulnerability in Atlassian's Confluence and Jira

CVE-2026-27826

What is CVE-2026-27826?

The MCP Atlassian server, used for managing contexts within Atlassian products like Confluence and Jira, is susceptible to an HTTP request smuggling vulnerability. This flaw allows unauthenticated attackers to manipulate the server into making outbound HTTP requests to URLs they control, simply by supplying crafted HTTP headers. The vulnerability resides in the middleware and dependency injection layers, evading detection during typical code analysis. This poses serious risks in cloud environments, potentially allowing attackers to retrieve sensitive IAM role credentials through instance metadata, as well as performing unauthorized internal network reconnaissance and executing injection attacks on results generated by LLM tools. To mitigate this issue, upgrading to version 0.17.0 or later is highly recommended.

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