MCP Atlassian: Path traversal in upload_attachment allows arbitrary file read (incomplete fix for CVE-2026-27825)

Summary

The confluence_upload_attachment and confluence_upload_attachments MCP tools accept a file_path parameter and do not validate that the path is confined to an allowed directory before opening the file. An attacker who can call these tools can read any file accessible to the MCP server process (SSH keys, .env files, API credentials) and exfiltrate it by uploading it to Confluence.

Note: The Jira upload_attachment mixin method in jira/attachments.py has the same missing validation, but it is NOT registered as an MCP tool in servers/jira.py and is therefore not currently reachable via MCP. It should still be patched to prevent future exposure if Jira upload tools are added.

This is an incomplete fix for CVE-2026-27825. That CVE was patched by adding validate_safe_path() to download operations (v0.17.0). The same protection was not applied to upload operations.

Details

validate_safe_path() is imported in both confluence/attachments.py and jira/attachments.py and is correctly called in all download functions. It is absent from the Confluence upload functions (which are exposed as MCP tools) and from the Jira upload mixin methods (which are not currently registered as MCP tools but should still be patched).

Download (protected — correctly patched):

# confluence/attachments.py:222-223
validate_safe_path(target_path)  # resolves symlinks + checks is_relative_to(cwd)

Upload (vulnerable — not patched):

# confluence/attachments.py:64-79 — NO validate_safe_path() call
if not os.path.isabs(file_path):
    file_path = os.path.abspath(file_path)  # normalizes but does NOT restrict
# ...
files = {"file": (filename, open(file_path, "rb"))}  # opens arbitrary file

Same pattern in jira/attachments.py:386.

Proof of Concept

# Call via MCP client
await session.call_tool("confluence_upload_attachment", {
    "content_id": "12345",
    "file_path": "/home/user/.ssh/id_rsa"  # absolute path — no traversal needed
})
# SSH private key is now a Confluence attachment
# Retrieve via: confluence_download_attachment or Confluence UI

Impact

Arbitrary file read from the server filesystem. High-value targets: SSH private keys, .env files, AWS/GCP credentials, database configuration, source code.

Fix

Add validate_safe_path(file_path) call in confluence/attachments.py:upload_attachment() (reachable via MCP) and jira/attachments.py:upload_attachment() (not currently reachable via MCP, but should be patched preventively), consistent with the existing download protection. No changes to validate_safe_path() itself are needed.

# Add after os.path.abspath() call:
try:
    validate_safe_path(file_path)
except ValueError as e:
    return {"success": False, "error": str(e)}