Supply Chain Advisory

Overview

Supply chain attacks bypass traditional code review by compromising upstream

dependencies. This skill provides patterns for detecting, preventing, and

responding to compromised packages in Python ecosystems.

When To Use

• After a supply chain advisory is published
• When auditing dependencies for a new or existing project
• During incident response for a suspected compromise
• When adding the SessionStart hook to a project

When NOT To Use

• General CVE triage unrelated to dependency supply chain
• Application-level vulnerability scanning (use a SAST tool)
• License compliance audits (different concern)

Known-Bad Versions Blocklist

The blocklist is at ${CLAUDE_SKILL_DIR}/known-bad-versions.json.

It is consumed by:

• SessionStart hook: warns per-session when compromised

versions detected

• make supply-chain-scan: CI/local scanning target
• This skill: manual audit guidance

Blocklist Format

{
  "package_name": [{
    "versions": ["x.y.z"],
    "date": "YYYY-MM-DD",
    "description": "What the attack did",
    "indicators": ["files or patterns to search for"],
    "source": "advisory URL",
    "severity": "critical|high|medium"
  }]
}

Adding a New Entry

• Add the entry to ${CLAUDE_SKILL_DIR}/known-bad-versions.json
• Add version exclusions (!=x.y.z) to affected pyproject.toml files
• Document in docs/dependency-audit.md under Supply Chain Incidents
• Run make supply-chain-scan to verify detection works

Quick Scan Commands

Check all lockfiles on machine for known-bad versions

# Scan uv.lock files for a specific compromised version
grep -r "package_name.*version" --include="uv.lock" /path/to/projects

# Search for malicious artifacts
find /path/to/projects -name "suspicious_file.pth" 2>/dev/null

# Check installed versions in virtualenvs
find /path/to/projects -path "*/.venv/lib/*/PACKAGE*/METADATA" \
  -exec grep "^Version:" {} +

Verify lockfile hash integrity

uv.lock includes SHA256 hashes for every package. If a package is

re-published with different content under the same version, uv sync

will fail with a hash mismatch. This is your strongest automatic defense.

Defense Layers

| Layer | Tool | Catches |

|-------|------|---------|

| Lockfile hashes | uv.lock SHA256 | Tampered re-published versions |

| Version exclusions | pyproject.toml != | Known-bad versions on fresh resolve |

| SessionStart hook | sanctum hook | Per-session warning for compromised deps |

| CI scanning | OSV, Safety | CVE database, and advisory matching |

| Artifact scanning | make supply-chain-scan | Malicious files (.pth, scripts) |

Limitations

• Zero-day supply chain attacks have no prior advisory: lockfile hashes

are the only automatic defense during the attack window

• Safety/CVE databases lag behind real-world compromises
• OSV provides broader coverage but is still reactive

Exit Criteria

• [ ] ${CLAUDE_SKILL_DIR}/known-bad-versions.json checked against

all lockfiles in scope; any match reported with package name,

bad version, severity, and advisory URL

• [ ] When a new known-bad entry is added: version exclusion

(!=x.y.z) added to the affected pyproject.toml, entry

documented in docs/dependency-audit.md, and

make supply-chain-scan run to confirm detection works

• [ ] uv.lock SHA256 hash integrity verified; uv sync failure

on hash mismatch surfaces as an explicit supply-chain warning

rather than a generic install error

• [ ] Artifact scan checks for malicious file patterns (.pth

files, unexpected scripts) in virtualenv paths before the

session proceeds