Binary SCA vs. Vendor Questionnaires: When Each One Earns Its Keep

A Fortune 500 insurer recently completed a 312-question security questionnaire with a SaaS vendor. The vendor scored 94%. Six months after deployment, the product was found to contain a statically linked OpenSSL build from 2020 with three unpatched CVEs, two of them network-reachable. The questionnaire had asked, in question 147, whether the vendor maintained current cryptographic libraries. The vendor had answered yes. They believed they did.

This is not a story about a dishonest vendor. It is a story about two tools that look interchangeable on a procurement checklist and are not.

Vendor questionnaires and binary SCA for procurement are both used to gate third-party software purchases. They answer different questions. Buying one when you needed the other is how regulated enterprises end up explaining themselves to auditors.

What Vendor Questionnaires Are Actually Good At

Questionnaires measure organizational maturity. They tell you whether the vendor has a CISO, a vulnerability disclosure process, an SDLC document, a SOC 2 report, and a story about how they handle incidents.

That information has value. A vendor with no security program is a different risk than a vendor with a mature one. Questionnaires let you sort vendors into rough tiers cheaply and at scale.

What they cannot do is tell you what is inside the binary. Every questionnaire answer is a self-attestation. The vendor is describing their intentions, their processes, and their beliefs. None of those are the artifact you are about to install on your network.

What Binary SCA Is Actually Good At

Binary SCA opens the artifact. It identifies the components statically and dynamically linked into the executable, matches them against vulnerability databases, and produces an inventory of what is actually there.

Done well — meaning with exploitability context, not raw CVE counts — it tells you whether the specific build in your procurement queue contains components with known weaknesses, whether those weaknesses are reachable in the deployed configuration, and whether the license posture matches what the contract claims.

Done poorly, it produces a 4,000-row spreadsheet of unranked CVE matches that no TPRM team has the headcount to triage. This is the failure mode of most off-the-shelf scanners, and it is why buyers have started treating binary SCA as noise.

When Each One Is Sufficient

Vendor questionnaires are sufficient when:

• The vendor is a low-blast-radius SaaS that never touches production data
• You are doing initial-tier sorting across hundreds of vendors
• The contract value and risk exposure do not justify deeper review
• A regulator has accepted self-attestation as the bar (rare, and shrinking)

Binary SCA is required when:

• The product runs inside your perimeter — appliances, agents, firmware, on-prem software
• The vendor will have privileged access to regulated data
• The contract is large enough that a wrong call shows up in board materials
• CRA, EO 14028, FDA premarket, or NIS2 obligations apply
• The procurement gate is the last point at which you can negotiate or walk

If the deal is in the second category and you are relying on a questionnaire alone, you are documenting due diligence rather than performing it.

Why the Combination Is Not the Answer Either

The instinct is to do both. Send the questionnaire, run a scanner, staple them together, ship to the GRC team.

This fails for a specific reason. Off-the-shelf binary scanners produce findings that require expert interpretation to act on. A TPRM analyst staring at 1,800 CVE matches with no exploitability ranking cannot defend a ship/no-ship decision to a CISO, a regulator, or a board. They will either escalate everything (paralyzing procurement) or rubber-stamp everything (defeating the point).

The Pre-Procurement Binary Autopsy exists to close exactly that gap. Two weeks, the actual vendor artifact, exploitability-ranked findings, and a one-page signed verdict — ship, do not ship, or ship with named conditions. The questionnaire tells you who the vendor is. The autopsy tells you what they are about to hand you.

The Procurement Reality

Most regulated buyers do not need binary-level review on every vendor. They need it on the ten to thirty vendors per year whose products will run inside the perimeter and whose failure would be a board-level event. For everyone else, a questionnaire is fine.

The discipline is knowing which is which before the contract is on the desk. Binautopsy works with TPRM teams who have stopped pretending questionnaires are evidence on the deals where evidence actually matters.