MCP Atlassian: Arbitrary file read/exfiltration via upload_attachment missing validate_safe_path()

Summary

The upload_attachment method in confluence/attachments.py reads and uploads arbitrary local files to Confluence without calling validate_safe_path(). Both download methods (download_attachment at line 223, download_content_attachments at line 272) correctly call validate_safe_path() before writing files, but the upload path at lines 35-79 skips this check entirely.

An AI agent connected via MCP (or an attacker influencing that agent through prompt injection) can read any file on the host and exfiltrate it by uploading it as a Confluence page attachment.

Vulnerable Code

File: src/mcp_atlassian/confluence/attachments.py, lines 62-79

# No validate_safe_path() call anywhere in this method
if not os.path.isabs(file_path):
    file_path = os.path.abspath(file_path)

if not os.path.exists(file_path):
    return {"success": False, "error": f"File not found: {file_path}"}

filename = os.path.basename(file_path)
attachment = self._upload_attachment_direct(
    content_id, file_path, filename, comment, minor_edit
)

The validate_safe_path function is already imported at line 9 of the same file, and used in the download methods. It was just not added to the upload path.

Proof of Concept

Tested with mcp-atlassian 0.21.1 on Python 3.11 (EC2, Amazon Linux 2023).

import inspect
from mcp_atlassian.confluence.attachments import AttachmentsMixin

# Confirm: no validate_safe_path in upload
source = inspect.getsource(AttachmentsMixin.upload_attachment)
assert "validate_safe_path" not in source  # passes

# Confirm: validate_safe_path IS in downloads
assert "validate_safe_path" in inspect.getsource(AttachmentsMixin.download_attachment)  # passes
assert "validate_safe_path" in inspect.getsource(AttachmentsMixin.download_content_attachments)  # passes