MCP Atlassian is a Model Context Protocol server for Atlassian products such as Confluence and Jira. In versions before 0.22.0, the upload tools for Jira and Confluence interpret caller-controlled path arguments on the MCP server and open those files before sending them as attachments. This allows a permitted client in remote or multi-user deployments to disclose files on the host system without requiring shell or direct filesystem access. The vulnerability is traced through the code paths AttachmentsMixin.upload_attachment, AttachmentsMixin.upload_attachments, file_path, file_paths, and jira update_issue. The vulnerability is identified as CWE-73 (External Control of File Name or Path) and has a CVSS 4.0 score of 8.3, indicating high severity. The issue is resolved in version 0.22.0.

An attacker with permitted client access can disclose arbitrary files on the host system by controlling file path arguments during attachment uploads. This can lead to unauthorized information disclosure without needing shell or direct filesystem access. The vulnerability affects confidentiality but does not indicate impact on integrity or availability.

Upgrade MCP Atlassian to version 0.22.0 or later, where this vulnerability is fixed. No other mitigation is indicated by the vendor advisory. Patch status is confirmed fixed in 0.22.0.