Summary
PrefectHQ/fastmcp v2026-03-26 was classified as CRITICAL RISK with a risk score of 2049. Sigil detected 237 findings across 1319 files, covering phases including provenance, network exfiltration, obfuscation, code patterns, install hooks, credential access. Review the findings below before installing this package.
Package description: 🚀 The fast, Pythonic way to build MCP servers and clients.
v2026-03-26
26 March 2026, 15:13 UTC
by Sigil Bot
Risk Score
2049
Findings
237
Files Scanned
1319
Provenance
Repository
https://github.com/PrefectHQ/fastmcpScanned From
https://github.com/PrefectHQ/fastmcp.gitFindings by Phase
Phase Ordering
Phases are ordered by criticality, with the most dangerous at the top. Click any phase header to expand or collapse its findings. Critical phases are expanded by default.
install-pip-setup-exec
CRITICALsetup.py executes code at install time
repo/src/fastmcp/cli/run.py:274
env_command_builder: An optional callable that wraps a command list
with environment setup (e.g. ``UVEnvironment.build_command``).
extra_args: Extra arguments forwarded after the module name.Why was this flagged?
This setup.py calls subprocess, os.system, exec, or eval during package installation. Legitimate packages rarely need to execute arbitrary commands at install time. This pattern is commonly used by malicious packages to download and run payloads, exfiltrate environment variables, or establish persistence. Rated CRITICAL because it runs with the installer's full permissions.
install-makefile-curl
HIGHMakefile/script pipes remote content to shell
repo/src/fastmcp/utilities/mcp_server_config/v1/environments/uv.py:121
"uv is not installed. Please install it with: "
"curl -LsSf https://astral.sh/uv/install.sh | sh"
)Why was this flagged?
A script or Makefile pipes content from a remote URL directly into a shell (curl | sh or wget | bash). This is inherently dangerous because the remote content can change at any time, and the command runs with the current user's permissions. Rated HIGH because it requires manual execution (unlike install hooks) but still executes arbitrary remote code.
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Markdown
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