The verdict in three sentences
A B2B web app security audit costs between 4,000 and 15,000 EUR in 2026, depending on the tested scope and pentest depth. The essential deliverable is not the list of vulnerabilities but the prioritized remediation plan aligned with the OWASP Top 10, with an estimate of fix costs. Expect 1 to 3 weeks for the audit and budget a fix cost often equal to the audit itself.
What the scope covers
A serious audit does not just run automated scans. It combines automated and manual testing on sensitive areas: authentication, session management, API, access control, injection, data exposure. The wider the scope, the higher the price.
| Tested scope | 2026 cost (EUR) | What is checked |
|---|---|---|
| Authentication and sessions | 1,000 - 3,000 | Password strength, MFA, tokens |
| REST/GraphQL API | 1,500 - 4,500 | Authorization, rate limiting, injection |
| Access control (IDOR) | 1,200 - 3,500 | Horizontal and vertical access |
| Data protection (GDPR) | 1,000 - 3,000 | Encryption, logs, retention |
| Infrastructure and headers | 800 - 2,500 | CSP, HTTPS, server config |
| Report and remediation plan | 800 - 2,000 | Prioritization, fix cost estimate |
One-off or recurring audit
A one-off audit before go-live is the minimum. But an app that changes every month deserves a recurring setup: each major release potentially introduces new vulnerabilities. Recurring costs more per year but drastically reduces incident risk.
| Criterion | One-off audit | Recurring audit |
|---|---|---|
| Cost | 4,000 - 15,000 EUR | 8,000 - 25,000 EUR/year |
| Frequency | Once (before prod) | Quarterly or per release |
| Coverage of changes | No | Yes |
| Fix retest | Optional (+800-1,500 EUR) | Included |
| Suited to | Stable project | Continuously evolving app |
| Compliance (attestation) | One-off | Continuous |
Mini case study
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Karim, IT director of a 140-employee logistics firm in Marseille, must secure a B2B client portal before launch. Scope: authentication, API, access control, GDPR. Chosen quote: 9,500 EUR, audit over 2 weeks, plus a 1,200 EUR retest. The audit reveals 3 critical flaws including an IDOR exposing other clients' invoices. Cost of a data breach as estimated by regulators and insurers: easily 50,000 to 200,000 EUR between fines, notification, and lost trust. Investing 10,700 EUR to eliminate this risk before launch is an obvious trade-off.
FAQ
What is the difference between an audit and a pentest? An audit reviews configuration and code, a pentest simulates a real attack. A good B2B app audit combines both, which explains the 4,000 to 15,000 EUR range.
How much do fixes cost? As an order of magnitude, budget a remediation cost of 50 to 120% of the audit cost, depending on the number and severity of flaws found.
Is an audit mandatory for GDPR? GDPR requires appropriate security measures but does not prescribe a formal audit. In practice, an audit is the best way to prove due diligence in case of inspection.
How long does an audit take? From 1 week for a narrow scope to 3 weeks for a complex app with API and multiple roles. The report is delivered a few days after testing.
Should you re-audit after fixes? Yes, a retest is strongly recommended (800 to 1,500 EUR) to verify flaws are closed and no regression was introduced.
Let's scope your project. Describe your application (stack, API, roles, sensitive data) and your go-live deadline, and we will price the audit and 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.
