The verdict in three sentences
An unaudited B2B web application exposes your company to a data-breach risk whose median cost exceeds 40,000 EUR for an SME. An OWASP Top 10 audit costs between 3,000 and 10,000 EUR and wraps up in 3 to 6 weeks. The real security budget is the audit plus remediation plus ongoing security maintenance: budget 6,000 to 18,000 EUR in year one.
What an application security audit costs in London
Price depends on attack surface: number of API endpoints, user roles, third-party integrations, presence of payment. Here are practical 2026 orders of magnitude for London.
| Application type | Audited scope | Audit price | Timeline |
|---|---|---|---|
| Simple internal app | 1 role, < 20 endpoints | 3,000 - 4,500 EUR | 3 weeks |
| Standard business SaaS | 3-4 roles, REST API | 5,000 - 7,000 EUR | 4 weeks |
| Multi-tenant platform | RBAC, payment, third parties | 7,000 - 10,000 EUR | 5-6 weeks |
| Audit + grey-box pentest | Intrusion tests included | 9,000 - 15,000 EUR | 6 weeks |
A serious audit covers the OWASP Top 10: injection, broken authentication, sensitive data exposure, misconfiguration, broken access control, SSRF, vulnerable components. The deliverable is a report ranked by severity (critical / high / medium / low) with proof of concept and a costed remediation plan.
OWASP checklist and remediation costs
Every vulnerability found carries a fix cost. Here is a 2026 remediation grid by flaw family.
| Remediation | Effort | Cost |
|---|---|---|
| MFA + password policy | 2-4 days | 1,200 - 2,800 EUR |
| Encryption at rest + in transit (TLS 1.3) | 2-3 days | 1,000 - 2,200 EUR |
| Access-control hardening (RBAC) | 3-6 days | 1,800 - 4,500 EUR |
| Injection fixes / parameterised queries | 2-5 days | 1,200 - 3,500 EUR |
| Security headers (CSP, HSTS, X-Frame) | 1 day | 400 - 900 EUR |
| Logging + SIEM alerting | 3-5 days | 1,800 - 4,000 EUR |
In practice, a London SME spends 2,000 to 8,000 EUR on remediation after a first audit. Then security maintenance of 400 to 900 EUR/month covers CVE monitoring, dependency updates, certificate renewal and an annual re-audit.
Mini case study
Thomas, CISO of a 90-employee industrial SME in Croydon, runs a supplier ordering portal. Audit at 6,500 EUR, surfacing 3 critical flaws (horizontal access control, no MFA, obsolete dependency). Remediation: 5,200 EUR. He subscribes to security maintenance at 650 EUR/month. Year-one total: 6,500 + 5,200 + 7,800 = 19,500 EUR. A breach exposing his supplier file would have cost, between regulator notification, lost contracts and emergency remediation, an estimated 45,000 to 70,000 EUR. Security ROI is reached with the first incident avoided.
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FAQ
How much is an OWASP audit in London in 2026 ?
Budget 3,000 to 10,000 EUR depending on attack surface. An audit with grey-box pentest rises to 15,000 EUR for a critical platform.
How long for a full audit ?
Between 3 and 6 weeks: one to two weeks of testing, one of writing, then debrief. Remediation adds 2 to 4 weeks.
Is MFA really essential ?
Yes. Per 2026 field data, enabling MFA blocks over 99 % of stolen-credential attacks. Its implementation cost (1,200 to 2,800 EUR) is negligible against the risk.
How much does a data breach cost an SME ?
The 2026 median order of magnitude sits between 40,000 and 70,000 EUR for an SME, including regulator fines and commercial losses, before reputational damage.
Do I need an annual audit ?
Yes, an annual re-audit (2,000 to 4,000 EUR) is recommended because new CVEs appear every week and the code evolves.
Let's scope your project. Give us the scope (number of roles, APIs, payment), your indicative budget and target timeline, and we'll frame the right OWASP audit. 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.
