Incomplete Path Traversal Fix in mcp-atlassian Allows RCE
An incomplete path traversal fix in the mcp-atlassian Python package allows attackers to overwrite application source modules and achieve remote code execution via a Confluence attachment upload.
CVE search metadata
CVE search record: CVE-2026-77271. KEV: no. Brief: Incomplete Path Traversal Fix in mcp-atlassian Allows RCE. Brief link: https://feed.craftedsignal.io/briefs/2026-09-mcp-atlassian-traversal/
The mcp-atlassian package (versions 0.17.0 through 0.21.0) contains an incomplete path traversal fix for CVE-2026-77271. The utility function validate_safe_path() is intended to prevent unauthorized file writes; however, it defaults to os.getcwd() when a base_dir is not explicitly provided. In typical containerized deployments, the working directory is the application root (e.g., /app), meaning the validation logic inadvertently allows file operations within the source code directory. An attacker with existing write access to a Confluence instance can leverage the confluence_download_attachment MCP tool to overwrite critical Python source modules. Subsequent process restarts or module reloads execute the injected malicious code, leading to full remote code execution.
Attack Chain
- Att