pkgxray

Supply-chain security for AI agents, npm packages, and Model Context Protocol (MCP) servers.

Analyze packages before you install them. Zero-dependency Node, runs entirely on your machine, never executes untrusted code.

Static analysis · Supply-chain intelligence · Prompt-injection detection · MCP security · Zero dependencies · Evidence-based verdicts · SAFE / REVIEW / BLOCK

Quick start

npm install -g pkgxray        # or zero-install: npx pkgxray …

pkgxray guard npm:[email protected]

Decision: **SAFE**

Verdict: **SAFE**
Grade: **A+** (99/100)

No high- or medium-risk indicators were found in the provided evidence.

Notes:
- **INFO npm-vs-github-clean** — npm tarball matches the linked GitHub repo
  at the published version. (15/16 files match GitHub @4.21.0)

Parameter grades:
- `knownVulnerabilities`: A+ (100/100)   - `provenance`: A+ (100/100)
- `dataAccess`: A+ (100/100)             - `persistence`: A+ (100/100)
- `obfuscation`: A+ (100/100)            - `injectionResistance`: A+ (100/100)
…

Real output, abridged. A BLOCK verdict instead lists every finding with the file and evidence that produced it.

Point it at a package, get a SAFE / REVIEW / BLOCK verdict with cited evidence — before a single line of that package runs. The guard flow stages the package in a sandboxed quarantine, audits the staged copy, and only promotes it when policy allows. It never runs npm install, lifecycle scripts, build steps, or package code.

guard blocking a malicious sample from the calibration corpus (modeled on the 2024 @solana/web3.js compromise) — the HIGH finding cites the exact wallet-read + exfiltration code. Real run; see how each screenshot was made.

Why pkgxray?

AI coding assistants increasingly install packages automatically, often without a human ever reading the code. Traditional antivirus inspects what executes; pkgxray inspects what gets installed.

Vulnerability scanners like npm audit and OSV-Scanner answer an essential question — does this package have a known CVE? — and pkgxray asks it too (via OSV, before anything downloads). But a freshly trojaned package has no CVE yet. So pkgxray also analyzes trust:

• What does the code actually do — read credentials? persist? phone home?
• Does the published npm artifact match the tagged GitHub source?
• Is the provenance attestation consistent with the claimed repository?
• Is there a prompt-injection payload aimed at the AI agent reading the docs?

It is intentionally conservative: it only reports evidence it can cite, its verdicts come from deterministic heuristics (no LLM in the verdict path, so injected text can't steer them), and its zero-false-block calibration is regression-gated in CI.

[!NOTE] pkgxray is designed to run alongside npm audit and OSV-Scanner, not replace them. See the comparison table below.

Key features

Supply-chain intelligence

• Known-CVE pre-check — batch OSV query that blocks before download
• Provenance verification — sigstore / SLSA attestations, cross-checked against the claimed repository
• Artifact divergence — the published npm tarball diffed against the tagged GitHub source
• Registry metadata signals — nonexistent or mismatched repos, attestation/repo inconsistencies (typosquat and impersonation indicators)
• Continuous monitoring — pkgxray recheck diffs installed deps against a stored verdict baseline and pre-vets newer versions, catching the maintainer-takeover / trojaned-update case

Static behavior analysis

• Credential & secret access — .ssh, .aws, .npmrc, .env, keychains, wallets — including paths assembled from split fragments (".s"+"sh")
• Persistence — writes to shell rc files, cron, launch agents
• Obfuscation + execution — a packed blob decoded into eval / new Function / vm
• Behavioral correlation — cross-file exfiltration, stage-2 loaders, download→execute (curl | sh), process.env harvesting near a network sink, on-chain command channels (EtherHiding), hidden self-node -e
• Trojan Source — bidi / zero-width Unicode attacks
• Opt-in behavioral canary — pkgxray canary executes a package's lifecycle scripts in an OS sandbox with decoy credentials. It can confirm malice; by design it never clears a package.

Prompt-injection detection

• Tiered detection in docs, code comments, and package.json metadata
• Delivery-envelope matching — instructions smuggled in invisible Unicode tag characters ("ASCII smuggling") or base64-encoded in docs/comments. Detecting the envelope, not the wording, generalizes past rewording.
• Injection-proof by construction — verdicts are deterministic; no model reads the package, so injected text can't steer the scanner. Full stance: threat model — on prompt injection.

MCP security

• MCP server — pkgxray-mcp gives any MCP-capable agent four audit tools
• Connect-time vetting — pkgxray mcp performs a read-only handshake and audits the tool manifest: injection in tool descriptions, concealed envelopes, and capability-surface mismatch (a get_weather that also takes a command)
• Pin & recheck — --pin fingerprints an approved manifest; --recheck catches the rug-pull

Runtime protection

• Per-call gate — pkgxray mcp-proxy wraps a live MCP server on the wire: denied tools stripped from listings, ~0.05 µs per-call verdict lookup, immediate re-audit on manifest change, injection scan of tool results, drift-after-pin denial
• Install gate — a hookshot hook binary intercepts an agent's shell command and runs pkgxray guard on every package about to be installed, across Claude Code, Cursor, Windsurf Cascade, Factory Droid, and OpenAI Codex (examples/hookshot/)

Policy engine

• One policy file, every surface — the CLI, MCP server, and proxy read the same .pkgxray.json through the same loader; policy can't drift
• Tighten freely, loosen loudly — stricter without limit; every loosening is explicit and printed in the report
• Enforced invariants — an allow must be pinned to name@version + sha256; a published CVE can never be muted or allowed away
• Fail closed — zero config means maximum strictness; a scan that errors becomes review, never safe

Architecture

Acquisition (OSV pre-check → fetch) → sandboxed quarantine → static analysis → policy → verdict. The same engine backs every surface: CLI, MCP server, runtime proxy, install hook, browser extension, and CI cache server.

Design principles: never execute untrusted code · report only citable evidence · explainability over black-box scoring · minimize false positives · operate offline whenever possible · zero runtime dependencies.

Details: docs/architecture.md · docs/design.md

Verdicts

Every signal resolves to one of three verdicts:

| Verdict | Meaning | You should | |---|---|---| | 🟢 SAFE | No high- or medium-risk indicators. | Install. (Only safe promotes out of quarantine by default.) | | 🟡 REVIEW | Incomplete evidence, or a privileged capability that needs a human — install scripts, computed eval, a lone callback domain, npm↔GitHub divergence. | Inspect the quarantined copy before promoting. --policy allow-review promotes review-grade if you accept that. | | 🔴 BLOCK | High-severity, cited evidence — prompt injection, credential access, persistence, obfuscation + execution, likely exfiltration, or a known CVE. | Do not install. Every finding names the file and evidence. |

Exit codes are stable and CI-friendly: 0 safe/allow · 2 block · 3 review. The exact mapping of every signal to block / review / info is specified in the severity policy.

Who is this for?

• AI developers — building agents that install packages or connect to MCP servers
• Security engineers — vetting third-party code with citable evidence
• DevSecOps — enforcing supply-chain policy in CI with stable exit codes and additive-only JSON
• Open-source maintainers — verifying their own dependency trees and release provenance
• Organizations adopting AI coding assistants — putting a deterministic gate between the agent and the registry

Use cases

Vet an npm package before installing

pkgxray guard npm:[email protected]
pkgxray guard npm:[email protected] --format json

# Guard a local extension and promote it only if policy allows
pkgxray guard ./ext --promote-to ./approved/ext

Vet an MCP server before connecting

# Static package scan FIRST, then read-only manifest audit
pkgxray mcp --package npm:[email protected] npx some-mcp-server

pkgxray mcp https://mcp.example.com/mcp     # HTTP server
pkgxray mcp --pin --package npm:[email protected] npx some-mcp-server
pkgxray mcp --recheck npx some-mcp-server   # catch the rug-pull

Full MCP guide (server, adapter, runtime proxy): docs/mcp.md

Enforce in CI/CD

pkgxray audit package-lock.json           # also: yarn.lock, pnpm-lock.yaml, package.json
pkgxray audit package-lock.json --deep    # full static/GitHub layer on each blocked dep

# Scheduled: has anything I already depend on become unsafe since install?
npx pkgxray recheck package-lock.json --format json

recheck exits non-zero only on a regression (a dep whose verdict got worse), which makes it a clean scheduled job — a ready-made GitHub Actions workflow is in the reference. Point PKGXRAY_CACHE_URL at the self-hostable cache server to collapse duplicate fetches across runners.

Guard AI coding agents

{ "mcpServers": { "pkgxray": { "command": "pkgxray-mcp" } } }

Give the agent the audit tools directly (above), gate its installs with the hookshot integration, and wrap its MCP servers with pkgxray mcp-proxy.

Security reviews

pkgxray --file examples/evidence.json --format json   # audit supplied evidence

Every verdict is a structured, citable report (schemaVersion: 1, additive-only — schema), and the quarantined copy is left on disk for manual inspection on review.

Configuration

One optional .pkgxray.json, read by every surface. Zero config is fully safe — an absent file means maximum strictness.

{
  "policy": "safe-only",              // or "allow-review" (a loosening — warns)
  "failOn": "review",                 // CI exit threshold
  "scanErrorPolicy": "fail-closed",   // a scan that errors → review, never safe

  "allow": [
    { "pkg": "[email protected]", "sha256": "e0b0…",
      "reason": "reviewed 2026-07", "expires": "2026-10-01" }
  ]
}

Precedence, the mute / mcp blocks, and the enforced invariants: docs/configuration.md · .pkgxray.example.json

Screenshots

All captures are real runs — reproduction steps for each are in docs/screenshots/.

CLI — pkgxray guard clearing express, with the npm↔GitHub cross-check

MCP proxy — a live session against a malicious demo server

Two tools stripped at tools/list — one for capability-surface mismatch, one for injection in its description; the denied tools/call never reaches the server.

hookshot install gate — an agent's npm install denied with cited evidence

Browser extension — the local MV3 popup blocking a risky sample

Comparison

npm audit and OSV-Scanner are excellent at what they target — matching your dependencies against known vulnerabilities. pkgxray overlaps with them on that layer and adds the layers they don't attempt:

| Capability | npm audit | OSV-Scanner | pkgxray | |---|:-:|:-:|:-:| | Known-CVE lookup | ✅ | ✅ | ✅ (OSV, blocks before download) | | Lockfile / project scanning | ✅ | ✅ | ✅ | | Registry signature / provenance verification | ✅ (npm audit signatures) | — | ✅ (sigstore/SLSA + repo cross-check) | | Static analysis of package code behavior | — | — | ✅ | | Prompt-injection & Unicode-smuggling detection | — | — | ✅ | | npm ↔ GitHub artifact divergence | — | — | ✅ | | Pre-install quarantine of a single package | — | — | ✅ | | Verdict-drift monitoring vs. a stored baseline | — | — | ✅ | | MCP server vetting & per-call runtime gating | — | — | ✅ |

Scoped to npm supply-chain vetting; based on each tool's public documentation at time of writing. OSV-Scanner covers many ecosystems beyond npm, which pkgxray does not.

Threat coverage

| Threat | Coverage | How pkgxray sees it | |---|:-:|---| | Credential theft | ✅ | reads of .ssh / .aws / .npmrc / .env / keychains / wallets, incl. split-fragment paths | | Prompt injection | ✅ | tiered detection in docs, comments, metadata; deterministic verdict path can't be steered by injected text | | Unicode smuggling | ✅ | invisible tag-block characters ("ASCII smuggling") + Trojan Source bidi / zero-width | | Base64 payloads | ✅ | encoded envelopes in docs/comments; blobs decoded into computed-arg eval / new Function / child_process | | Persistence | ✅ | writes to shell rc files, cron, launch agents | | Obfuscation | ✅ | packed blob + computed-arg execution; minification alone is deliberately not flagged | | Known CVEs | ✅ | OSV batch pre-check before download; never mutable by config | | Trojaned updates / maintainer takeover | ✅ | recheck verdict-drift + version-drift monitoring | | Artifact divergence | ✅ | published npm tarball diffed against the tagged GitHub source | | Dependency confusion | ◑ | the out-of-band callback beacons confusion payloads use are flagged; registry resolution itself belongs to your package manager | | Typosquatting | ◑ | surfaced via repo-mismatch (package.json → nonexistent/mismatched repo) and provenance-mismatch signals; no name-similarity heuristic | | MCP capability abuse | ✅ | capability-surface mismatch in the manifest audit | | Runtime tool drift | ✅ | mcp-proxy re-audits on tools/list_changed; pinned-manifest drift is denied |

✅ detected · ◑ partial / indirect

[!IMPORTANT] Known blind spot: pkgxray reasons about bytes in the tarball. A package that downloads its real payload after install can ship a clean tree. pkgxray flags the capability when its shape is unambiguous, but pair it with runtime/install-time sandboxing when that risk matters. Full analysis: docs/threat-model.md.

Performance

• Local static analysis: ~25 ms. Almost all of guard's wall-clock is network round-trips — a full guard of express / chalk / commander is ~1.3–1.5 s cold-cache (Apple M1, Node 26).
• Known-vulnerable packages block at the OSV pre-check, before download.
• mcp-proxy overhead: ~0.05 µs per tools/call decision; a full manifest re-audit (~1 ms per 30 tools) runs only when the manifest changes.
• Calibration — precision, recall, and the 0-false-block gate — is measured by a committed benchmark corpus that fails CI when it regresses.

Full numbers: docs/reference.md#performance · methodology: docs/benchmark.md

Roadmap

• [ ] List the MCP server in the public MCP registries
• [ ] Ship a reusable GitHub Action wrapping audit / recheck
• [ ] Publish the browser extension to the Chrome Web Store (today it loads unpacked)
• [ ] Replay documented known-malicious npm corpora against the engine and publish the results
• [ ] A --report evidence bundle for one-command false-block / missed-threat reports

The longer-form plan lives in the adoption playbook.

📖 Documentation

| Doc | What it covers | |---|---| | docs/architecture.md | Pipeline, surfaces, design principles, repo layout | | docs/threat-model.md | Scope, the known blind spot, false-positive philosophy, prompt-injection stance | | docs/mcp.md | MCP server, connect-time vetting, per-call runtime proxy | | docs/configuration.md | .pkgxray.json schema, precedence, invariants | | docs/reference.md | Severity policy, recheck monitoring, performance, JSON output, browser extension, cache server | | docs/benchmark.md | Calibration benchmark & real-world validation | | docs/compatibility.md | The 1.0 compatibility contract & stability tiers | | docs/json-schema.md | Full --format json schema | | docs/canary-threat-model.md | Threat model for the opt-in canary surface | | docs/design.md · docs/design/ | Design principles & internal working notes |

Start at the documentation index.

Development

npm test                 # zero-dep node --test suite
npm run benchmark        # calibration corpus: precision/recall + 0-false-block gate
npm run build:browser    # build the MV3 browser extension
npm run audit:evidence -- --file examples/evidence.json

The calibration benchmark runs a labelled corpus of malicious and benign fixtures through the real engine and fails on a false block or a missed detection. Repo layout is described in docs/architecture.md.

Security & license

Releases are published to npm with provenance (SLSA attestation), gated on the test suite, the calibration benchmark, and pkgxray's own supply-chain guard. To report a vulnerability in pkgxray itself, see SECURITY.md.

MIT