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Rule ID: AE-MCP-001 · Severity: High · Category: MCP Safety · Auto-fixable: Yes (partial) — charter fix --rule AE-MCP-001
AE-MCP-001 is partially auto-fixable. Charter can bump unpinned or behind-stable packages to the catalog’s stable version. Deprecated or archived packages require manual migration — Charter provides the successor package name in the finding evidence, but will not rewrite the entry automatically.

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Why this rule

An MCP server at @latest can change behavior between runs without any change to the repo. A package can be deprecated, archived, or found to contain a known vulnerability after a repo first passed Charter. Pinning to an exact version ties the tool definition to a reviewable artifact — every tool-call behavior is deterministic across machines and runs.

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What triggers it

Charter scans MCP configuration files for server entries launched by package runners and checks whether each entry pins an exact version. Scanned files: .mcp.json, mcp.json, .cursor/mcp.json, .vscode/mcp.json, .gemini/settings.json Scanned runners: npx, bunx, uvx, pnpm dlx The finding ladder based on signal type:
SignalSeverityExample
Deprecated or archived packageHigh@modelcontextprotocol/server-github
Known CVE / GHSA advisory on pinned versionHighmcp-server-git@2025.8.0
Unpinned reference (@latest, semver range, missing version)Highmcp-server-git@latest
Behind catalog stable, no advisoryInformationalOld exact pin, no known issues
Unpinned forms that fire High: @latest, a missing version suffix, semver ranges (^1.0.0, ~1.0.0, >=1.0.0), floating git refs, or dynamic values like pkg@${VERSION}.

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Examples

.mcp.json (floating tag)
{
  "mcpServers": {
    "git": {
      "command": "npx",
      "args": ["-y", "mcp-server-git@latest"]
    }
  }
}
.mcp.json (archived package)
{
  "mcpServers": {
    "github": {
      "command": "npx",
      "args": ["-y", "@modelcontextprotocol/server-github@1.0.0"]
    }
  }
}

# @modelcontextprotocol/server-github is archived — fires High
# even though the version is pinned exactly

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How to fix

charter fix --rule AE-MCP-001 --dry-run
For unpinned or behind-stable packages, the auto-fixer updates the package spec to the catalog’s stable version as a diff-first preview before writing anything. For deprecated or archived packages, migration is manual — the finding evidence includes the recommended successor package name. Update the entry to use the successor at its current stable version.

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Score impact

Deprecated, unpinned, or advisory-covered findings are High (−10 each). The behind-stable-only nudge is Informational (0). No hard cap applies to MCP findings — caps are reserved for raw-secret findings.

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Edge cases

Package specs are resolved only for direct runners (npx, bunx, uvx) and the dlx subcommand of pnpm/yarn. Local path arguments (./, /, ../) and exec/run forms launch local binaries and are not treated as registry packages. Scoped packages (@scope/name@1.2.3) are pinned only when the trailing version is exact. A dynamic pkg@${VERSION} reference is treated as unpinned.
  • AE-MCP-002 — remote MCP server origins must be trusted
  • AE-MCP-003 — remote MCP servers must declare auth
  • AE-SEC-002 — no raw secrets in MCP config files

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CLI

charter explain AE-MCP-001