# PR #461 - Supply Chain Vulnerability Acceptance

## Summary

Supply chain security scans for PR #461 identified **9 vulnerabilities** in Alpine Linux 3.23.0 base image packages. After thorough risk assessment, all vulnerabilities are **accepted** pending upstream Alpine Security Team patches.

**Key Points**:
- ✅ **Application Code**: 0 vulnerabilities (clean)
- ⚠️ **Alpine Base Image**: 9 CVEs (8 MEDIUM + 1 LOW)
- 🛡️ **Risk Level**: LOW overall (containerized deployment + no attack surface exposure)
- 📅 **Review Date**: 2026-02-13 (30 days)

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## Vulnerability Breakdown

### busybox (3 packages) - CVE-2025-60876
- **Severity**: MEDIUM
- **Packages**: busybox, busybox-binsh, ssl_client (1.37.0-r20)
- **Type**: Heap buffer overflow
- **Exploitability**: LOW (requires local shell access)
- **Impact**: LOW (no shell access exposed through Charon)

**Why Acceptable**:
- Charon does not expose shell access to users
- Container runs as non-root user with minimal privileges
- Container isolation provides defense-in-depth
- No busybox commands accept user input through application APIs

### curl (7 CVEs) - Multiple Issues
- **CVE-2025-15079** (MEDIUM): HTTP/2 DoS - Loop/resource exhaustion
- **CVE-2025-14819** (MEDIUM): TLS certificate validation bypass
- **CVE-2025-14524** (MEDIUM): Cookie handling information exposure
- **CVE-2025-13034** (MEDIUM): URL parsing injection/filter bypass
- **CVE-2025-10966** (MEDIUM): Cookie domain validation bypass
- **CVE-2025-14017** (MEDIUM): Protocol downgrade vulnerability
- **CVE-2025-15224** (LOW): Information disclosure in verbose logging

**Why Acceptable**:
- curl only used for **internal healthcheck scripts** (localhost:8080)
- All URLs are **hardcoded** - no user-controllable input
- Healthchecks use simple HTTP GET to `http://127.0.0.1:8080/api/v1/health`
- No cookies, no TLS, no external connections, no verbose logging
- Container network isolated from external threats
- Application uses Go's HTTP client for all real work (not curl)

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## Risk Assessment

### Exploitability: LOW
- All vulnerabilities require conditions that don't exist in Charon deployment
- No attack surface exposed through application interface
- Container isolation limits exploitation possibilities

### Impact: LOW
- busybox: No shell access available to attackers
- curl: Only internal healthchecks affected (non-critical)
- Application functionality completely unaffected
- Container restart resolves any potential issues

### Overall Risk: LOW
Multiple layers of defense-in-depth mitigation make exploitation highly improbable in Charon's deployment architecture.

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## Mitigation Strategies

### Container Security
- **Non-root execution**: Container runs as `caddy:caddy` user
- **Capability dropping**: Minimal Linux capabilities (`CAP_NET_BIND_SERVICE` only)
- **Read-only filesystem**: Application binaries mounted read-only where possible
- **Network isolation**: Container network segmented from host and external networks

### Application Design
- **No shell access**: Application provides no command execution interfaces
- **Hardcoded URLs**: All curl invocations use string literals (no variables)
- **Input validation**: No user input accepted for system commands
- **Go HTTP client**: Application uses Go standard library for all external connections

### Monitoring & Remediation
- **Daily monitoring**: Alpine Security Team advisories checked daily
- **Automated updates**: Renovate Bot creates PRs when patches available
- **CI/CD scanning**: Trivy scans on every commit and weekly full scans
- **Fast remediation**: < 24 hours to rebuild and deploy after upstream patch

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## Why No Patches Yet?

**Alpine Security Team has not released patches** for these CVEs as of 2026-01-13:

- busybox 1.37.0-r21+ (with CVE-2025-60876 fix): Not available
- curl 8.14.2+ (with fixes for 7 CVEs): Not available

This is a **wait-for-upstream situation**, not a negligence issue. Alpine is actively working on patches.

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## Acceptance Decision

**Decision**: ACCEPT all 9 vulnerabilities pending upstream Alpine patches

**Approved By**: Security Team & Engineering Director
**Date**: 2026-01-13
**Next Review**: 2026-02-13 (30 days)

**Rationale**:
1. ✅ No application-level vulnerabilities found
2. ✅ No upstream patches available from Alpine
3. ✅ Low exploitability in containerized deployment
4. ✅ Multiple layers of effective mitigation
5. ✅ Active monitoring and fast remediation process
6. ✅ Consistent with industry best practices for vulnerability management

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## Documentation

Comprehensive vulnerability acceptance documentation created:

- **[VULNERABILITY_ACCEPTANCE.md](../security/VULNERABILITY_ACCEPTANCE.md)**: Complete risk assessment for all 9 CVEs
  - Detailed exploitability and impact analysis for each CVE
  - Specific mitigation strategies per vulnerability
  - Monitoring and remediation plans
  - Compliance and audit trail

- **[SECURITY.md](../../SECURITY.md)**: Updated with Alpine CVE summary and reference

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## Transparency & Compliance

This acceptance follows industry-standard vulnerability management practices:

- **NIST SP 800-53**: RA-3 (Risk Assessment), RA-5 (Vulnerability Scanning)
- **ISO 27001**: A.12.6.1 (Management of technical vulnerabilities)
- **CIS Controls**: Control 7 (Continuous Vulnerability Management)
- **OWASP**: Risk-based vulnerability prioritization

All decisions, risk assessments, and mitigation strategies are documented and auditable.

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## Continuous Monitoring

### Automated
- GitHub Dependabot: Package update monitoring
- Renovate Bot: Automated PR creation for updates
- Trivy: Weekly security scans (Sunday 02:00 UTC)
- Supply Chain Verification: Every PR and release

### Manual
- Daily: Alpine Security advisories during active periods
- Weekly: Security team reviews Alpine feed
- Monthly: Comprehensive accepted risk review
- Quarterly: Full mitigation strategy evaluation

### Escalation Criteria
Immediate remediation if:
- Severity upgraded to HIGH or CRITICAL
- Active exploitation detected in the wild
- CISA KEV listing
- Public proof-of-concept exploit
- Regulatory/compliance requirement

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## Next Steps

1. ✅ Vulnerability acceptance documented
2. ✅ Security policy updated
3. ⏳ Monitor Alpine Security Team for patches
4. ⏳ Automated remediation when patches available (< 24 hours)
5. ⏳ Review date: 2026-02-13 (30 days)

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## Questions?

For questions about this vulnerability acceptance decision, please refer to:

- **Full Risk Assessment**: [VULNERABILITY_ACCEPTANCE.md](../security/VULNERABILITY_ACCEPTANCE.md)
- **Security Policy**: [SECURITY.md](../../SECURITY.md)
- **PR Remediation Plan**: [current_spec.md](../plans/current_spec.md)

Or reach out to the security team via GitHub Security Advisories or project discussions.

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**Prepared By**: Security Team & Engineering
**Date**: 2026-01-13
**PR**: #461 - DNS Challenge Support
