fkie_cve-2026-77258

MCP Atlassian is a Model Context Protocol (MCP) server for Atlassian products (Confluence and Jira). Prior to 0.22.0, upload_attachment in src/mcp_atlassian/confluence/attachments.py accepts a caller-controlled file_path and opens the selected server-local file without restricting it to the workspace. A permitted Confluence MCP caller can upload the file as an attachment and disclose data readable by the server process. This issue is fixed in version 0.22.0.

GHSA-93xw-j965-9mx3 — MCP Atlassian: Arbitrary file read/exfiltration via upload_attachment missing validate_safe_path()

Affected: PyPI: mcp-atlassian

## 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

```python # 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).

```python import inspect from mcp_atlassian.confluence.attachments import AttachmentsMixin

# Confirm: no validate_safe_path in upload source = inspect.getsource(AttachmentsMix…

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fkie_cve-2026-77258

GHSA-93xw-j965-9mx3 — MCP Atlassian: Arbitrary file read/exfiltration via upload_attachment missing validate_safe_path()