Vetting open source telecom core network software before it goes anywhere near production traffic isn't optional anymore — it's the difference between a clean audit and a 3 a.m. incident call. Telecom cores run on a dense stack of open source: kernel modules, container runtimes, service meshes, 5G core network functions built on projects like free5GC or Open5GS, and dozens of transitive dependencies nobody remembers approving. A single unpatched or maliciously tampered package in that stack can propagate across every subscriber session it touches. This guide walks through a repeatable, seven-step process for vetting open source telecom core network components — from initial inventory through procurement sign-off and continuous monitoring — so you can move fast on adoption without inheriting risk you can't see.
Step 1: Build a Vetting Process for Open Source Telecom Core Network Software
Before you evaluate a single package, define what "vetted" means for your organization. This is the foundation of any telecom OSS due diligence process — without written criteria, vetting becomes ad hoc and inconsistent across teams evaluating different network functions.
At minimum, your policy should specify:
- Which layers require review (base OS images, CNFs/VNFs, orchestration tooling, CI/CD dependencies)
- Minimum acceptable license types (avoid copyleft licenses in proprietary NF code paths)
- Required provenance artifacts (SBOM, signed builds, reproducible build attestations)
- Escalation thresholds (e.g., any CVSS 9+ finding blocks merge automatically)
Document this in a policy-as-code file so it's enforceable, not just aspirational:
# vetting-policy.yaml
oss_policy:
require_sbom: true
max_cvss_score: 7.0
banned_licenses: [AGPL-3.0, SSPL-1.0]
min_scorecard_score: 6.0
require_signed_artifacts: true
Step 2: Generate a Complete Software Bill of Materials
You cannot vet what you cannot see. Every open source component entering your core — down to transitive dependencies pulled in by a CNF's container image — needs to be enumerated in an SBOM.
# Generate an SBOM for a CNF container image
syft packages docker:free5gc/upf:v3.4.2 -o cyclonedx-json > upf-sbom.json
# Cross-check against a second tool to catch enumeration gaps
trivy image --format cyclonedx --output upf-trivy-sbom.json free5gc/upf:v3.4.2
Diff the two outputs. Discrepancies usually point to statically linked binaries or vendored code that one scanner missed — both are common in telecom NFs written in Go or C, where vendoring is standard practice.
Step 3: Run Vulnerability and Malicious-Package Scanning
With an SBOM in hand, scan every component against multiple vulnerability databases. A single feed misses things; telecom cores are high-value targets and can't afford blind spots.
# Vulnerability scan against the SBOM
grype sbom:upf-sbom.json --fail-on high
# Cross-reference against OSV for broader ecosystem coverage
osv-scanner --sbom=upf-sbom.json
This is also the point to run malicious-package detection, not just known-CVE matching. Typosquatted packages and compromised maintainer accounts have hit npm, PyPI, and Go module proxies repeatedly — a network function open source risk review has to assume supply chain compromise, not just unpatched bugs, is in scope.
Step 4: Verify Provenance and Cryptographic Signatures
A clean scan on a package that isn't actually the package you think it is means nothing. Verify build provenance and signatures before trusting any artifact.
# Verify a container image signature with cosign
cosign verify --key cosign.pub free5gc/upf:v3.4.2
# Check SLSA provenance attestation
cosign verify-attestation --type slsaprovenance \
--key cosign.pub free5gc/upf:v3.4.2
If a project doesn't publish signed releases or provenance attestations, treat that as a finding in itself, not a minor gap. For core network infrastructure, unsigned artifacts from an unverifiable build pipeline should require compensating controls — internal re-signing after your own audit, or an explicit risk acceptance from security leadership.
Step 5: Assess Project Health and Maintainer Risk
Vulnerability scans tell you about known issues today; project health tells you about risk tomorrow. Check maintainer count, commit velocity, funding, and response time to prior CVEs.
# OpenSSF Scorecard gives a quick composite health signal
scorecard --repo=github.com/free5gc/free5gc --format json
Look specifically for: single-maintainer projects with no succession plan, long gaps between security patches, and dependencies that haven't had a release in 18+ months. A telecom core running for a decade will outlive plenty of the open source projects it's built on — factor that lifecycle mismatch into your risk scoring, not just point-in-time CVE counts.
Step 6: Run Protocol and Interop Testing in an Isolated Sandbox
Telecom-specific risk doesn't show up in generic vulnerability databases. Fuzz the actual signaling and data plane interfaces — N2/N3/N4 in 5G core, Diameter/SS7 in legacy cores, O-RAN's E2/A1 interfaces — in an isolated lab before anything reaches a live network.
# Example: fuzzing a PFCP interface with a protocol-aware fuzzer
python3 pfcp_fuzzer.py --target 10.20.0.5:8805 --iterations 50000 --log findings.json
Combine this with traffic replay from a staging core to confirm the component behaves correctly under real subscriber load patterns, not just synthetic test cases. Malformed-packet handling failures here are the class of bug that takes down a core, not just a container.
Step 7: Formalize Sign-Off With a Telecom Procurement Security Checklist
Every component that passes the previous six steps still needs a documented, auditable approval before it enters procurement or deployment pipelines. Build this into a telecom procurement security checklist that vendors and internal teams both work against:
- SBOM generated and archived with version pinning
- No unresolved critical/high CVEs, or documented compensating controls
- Signatures and provenance verified against publisher keys
- OpenSSF Scorecard score above policy threshold
- Protocol-level fuzz testing completed with findings triaged
- License reviewed and approved by legal
- Owner assigned for ongoing patch monitoring
Store this checklist alongside the artifact in your compliance system so it's retrievable during an audit or a post-incident review — auditors will ask for exactly this trail.
Troubleshooting and Verification
SBOM tools disagree on component counts. This is expected when static linking or vendored dependencies are involved. Run both a source-based scanner (syft against source) and a binary-based scanner (against the compiled artifact) and reconcile the union, not the intersection.
Scanner reports hundreds of low-severity findings and the team tunes it out. Set severity floors in your policy (Step 1) and route only actionable findings to engineering. Alert fatigue is the fastest way to make a vetting program get ignored.
Signature verification fails for an otherwise legitimate release. Check whether the project rotated signing keys — this happens after maintainer transitions. Confirm the new key through an out-of-band channel (project mailing list, GitHub security advisory) before trusting it, since this is also a known technique attackers use to slip in a compromised key.
A component passes vulnerability scanning but fails protocol fuzzing. Trust the fuzzing result. CVE databases lag real-world protocol behavior by months in telecom-specific software; a clean CVE scan on a PFCP or GTP implementation says nothing about how it handles a malformed packet.
Vetting takes so long that teams route around it. This is a process failure, not a security failure. Automate Steps 2–4 in CI so they run on every dependency bump rather than as a one-time manual gate, and reserve manual review for Steps 5–7.
How Safeguard Helps
Manually running this process across every CNF, container base image, and CI dependency in a telecom core doesn't scale — and telecom environments rarely have the luxury of a dedicated team doing nothing but open source review. Safeguard automates the full vetting pipeline described above: continuous SBOM generation across your build and runtime environments, multi-source vulnerability and malicious-package detection, signature and provenance verification, and OpenSSF Scorecard-style health scoring, all mapped to policy-as-code so findings block the pipeline automatically instead of waiting for a manual review cycle.
For telecom operators and NF vendors, Safeguard turns the telecom procurement security checklist into a living artifact — every component's approval status, scan history, and sign-off trail is queryable at audit time, and re-verified automatically whenever a dependency changes upstream. That means your telecom OSS due diligence process stays current as your core evolves, instead of documenting a snapshot that's stale within a quarter. If you're standardizing how your organization approaches vetting open source telecom core network components, Safeguard is built to be the system of record and enforcement layer behind that process, not just another dashboard to check manually.