The verdict in three sentences
A serious web application security audit ranges from 5,000 to 25,000 EUR (excl. tax) in 2026, depending on whether it is a quick black-box test or a full white-box pentest with code review. The cost is counted in person-days (600 to 1,200 EUR/day for a qualified consultant), not a magic flat fee. The real calculation isn't the audit price: it's the avoided cost of an exploited vulnerability (GDPR fine, downtime, lost client trust).
The three audit types and their cost
The chosen method drives the budget. A black-box test simulates an external attacker with no information; grey-box starts from a user account; white-box includes access to source code and architecture.
| Audit type | What the auditor knows | Typical duration | 2026 cost (EUR excl. tax) |
|---|---|---|---|
| Black-box | Nothing (external attacker) | 3-5 days | 3,000 - 6,000 |
| Grey-box | Standard user account | 5-8 days | 5,000 - 10,000 |
| White-box + code review | Source code + architecture | 8-15 days | 9,000 - 20,000 |
| Full application pentest | Grey-box + API + infra | 12-20 days | 12,000 - 25,000 |
| Automated scan only | Tools only | 1-2 days | 1,000 - 2,500 |
An automated scan alone never replaces a manual test: it detects known flaws, not business-logic errors (privilege bypass, cart manipulation, privilege escalation).
OWASP severity and fix prioritisation
The report ranks each vulnerability by severity (often via the CVSS score). Not all require an emergency fix: you must weigh effort against risk.
| Level | OWASP example | Recommended fix window | Estimated dev effort |
|---|---|---|---|
| Critical | SQL injection, RCE | Immediate (< 48 h) | 1-3 days |
| High | Broken access control | < 1 week | 1-2 days |
| Medium | Stored XSS, CSRF | 2-4 weeks | 0.5-1 day |
| Low | Missing headers | Next release | A few hours |
| Informational | Version disclosure | Optional | Minimal |
A good provider quotes not only the audit but a prioritised remediation plan with the fix cost of each batch.
The cost of an unfixed vulnerability
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This is the argument that justifies the budget to management. A single exploited flaw can cost far more than ten audits.
| Consequence | 2026 order of magnitude |
|---|---|
| Data-protection fine (GDPR breach) | Up to 4% of global revenue or 20M EUR |
| Service downtime (e-commerce) | 5,000 - 50,000 EUR/day of lost revenue |
| Breach notification + crisis handling | 15,000 - 80,000 EUR |
| Lost tender contract | Variable, often > 100,000 EUR |
| Restoration + forensics | 10,000 - 40,000 EUR |
Mini case study
Nicolas, IT Director of a mid-size industrial firm in Nantes, must go live with a client portal before responding to a large-account tender requiring proof of security. He commissions a grey-box pentest at 8,500 EUR (excl. tax) (8 days). The audit reveals two critical flaws (privilege bypass, API with no rate limiting), fixed in 4 dev-days (2,400 EUR). Total: 10,900 EUR excl. tax. The target contract is worth 350,000 EUR: without the audit attestation, the bid was disqualified outright. The ROI is immediate, and the report is reused for three more tenders the following year.
FAQ
How often should you re-audit? At minimum once a year for an exposed application, and systematically after a major change (new sensitive feature, migration). A continuous automated scan (a few hundred EUR/month) complements the annual manual audit.
Does a pentest guarantee no vulnerabilities? No. It gives a point-in-time snapshot within a defined scope. No serious auditor promises zero risk; it strongly reduces the attack surface and prioritises fixes.
Black-box or white-box? White-box finds more flaws for a comparable day-rate, because the auditor doesn't waste time mapping. For a first-time pre-tender check, grey-box offers the best coverage/price ratio (5,000-10,000 EUR excl. tax).
Do you need a certified provider? A certification (such as PASSI in France) reassures large accounts and is sometimes required in public tenders. For an SME, experience and the quality of the remediation report matter as much as the label.
Is the fix included in the audit? Rarely. The audit identifies and prioritises; the fix is a separate development task. Always request a quote covering the audit AND a remediation envelope for critical flaws.
Let's scope your project. Describe your application (stack, scope, tender deadline) and we'll frame the right audit, from a targeted scan to a full pentest with a costed remediation plan. Detailed quote within 48 h. WhatsApp +221 77 596 93 33.
Mohamed Bah
Fondateur, Kolonell
Passionate about digital and entrepreneurship in Africa, Mohamed has been helping Sénégalese businesses with their digital transformation since 2020. Founder of Kolonell, he believes every SME deserves a professional and accessible online présence.
