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CVE-2026-77262 – Arbitrary File Read (Path Traversal) – mcp-atlassian < 0.22.0

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Summary

CVE-2026-77262 is a high-severity (CVSS 8.6) path traversal / arbitrary file read vulnerability in sooperset/mcp-atlassian, a Model Context Protocol (MCP) server that exposes Jira and Confluence operations to AI agents and MCP clients. The confluence_upload_attachment tool passes an attacker-controlled file_path parameter directly to a file-open call with no path validation, allowing any file readable by the server process to be exfiltrated as a Confluence attachment. The flaw is an incomplete fix of an earlier advisory (GHSA-xjgw-4wvw-rgm4 / CVE-2026-27825), which restricted the download path but left the equivalent upload code path unguarded.

Technical details

  • Root cause: In src/mcp_atlassian/confluence/attachments.py, the confluence_upload_attachment tool (_upload_attachment_direct) opens the caller-supplied file_path with open(file_path, "rb") and streams it into a multipart upload with no call to the project’s own validate_safe_path() sanitization function — the same function already used to guard the confluence_download_attachment path.
  • Trigger conditions: Any MCP client (or an AI agent manipulated via prompt injection) that can invoke the confluence_upload_attachment tool can supply an absolute or relative path (e.g., /etc/passwd, SSH keys, cloud credential files, .env secrets) instead of a legitimate local file.
  • Attack vector: Network. The mcp-atlassian server commonly runs in streamable-http mode and binds to 0.0.0.0 by default, meaning unauthenticated or minimally-authenticated network access to the MCP endpoint can be sufficient to reach the vulnerable tool.
  • Impact: The targeted file’s contents are read by the server process and uploaded to a Confluence page as an attachment, giving the attacker a covert exfiltration channel disguised as normal attachment traffic. The vulnerability affects confidentiality only (no integrity or availability impact).

Affected software

  • sooperset/mcp-atlassian (PyPI package mcp-atlassian) — all versions prior to 0.22.0

Severity

  • CVSS v3.1 Base Score: 8.6 (High)
  • Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N
  • CWE-22: Improper Limitation of a Pathname to a Restricted Directory (Path Traversal)

Mitigation and recommended actions

  • Immediate: Upgrade mcp-atlassian to version 0.22.0 or later, which applies validate_safe_path() (or equivalent path confinement) to the upload code path, matching the protections already present on the download path.
  • If immediate patching is not possible:
    • Restrict network access to the mcp-atlassian server/MCP endpoint to trusted hosts only; avoid binding to 0.0.0.0 in streamable-http mode.
    • Place the service behind authentication and network access controls (VPN, firewall allow-lists, reverse proxy with authentication) so untrusted clients cannot reach the confluence_upload_attachment tool.
    • Monitor/restrict outbound Confluence attachment uploads for anomalous file paths or unexpected file types.
    • Run the mcp-atlassian process with least-privilege file-system permissions to limit the blast radius of any successful file read.

References

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