Technical debt isn’t just an engineering problem. It’s a security risk.
Left unchecked, it increases the likelihood of data breaches, drives up incident costs, and quietly drains productivity across your entire organisation. Most leadership teams know technical debt slows delivery. Far fewer realise the cost of technical debt also expands the attack surface and makes every incident harder – and more expensive – to fix.
What is technical debt (in security terms)?
Technical debt is the result of choosing speed today over maintainability tomorrow. In security terms, it’s the buildup of shortcuts, outdated systems, and postponed fixes that leave gaps attackers can exploit.
Not all technical debt carries the same risk. Some are intentional and manageable – quick prototypes or minimum viable products (MVPs) that are designed to be cleaned up later.
Security debt is different. It includes things like:
- Unpatched vulnerabilities
- Legacy frameworks that are no longer supported
- Unsupported infrastructure running critical services
- Weak or outdated authentication mechanisms
- Long-standing misconfigurations that create entry points
So why does security debt pile up? Usually, feature delivery wins. Risks are underestimated, fixes are deferred, and problems only get addressed once something breaks. Teams often know the debt exists, but lack the time, budget, or executive backing to reduce technical debt before it becomes a serious risk.
What is the hidden cost of technical debt?
The real cost of technical debt goes well beyond slower development. It compounds across security, finances, and operations – the longer it’s ignored, the harder it becomes to unwind.
Direct security impact
Security debt increases your attack surface in very real ways:
- Outdated dependencies often contain known vulnerabilities that attackers actively target.
- Unsupported systems don’t receive patches at all, leaving them permanently exposed.
- Misconfigurations accumulate as systems evolve without consistent review.
When a zero-day vulnerability hits, high-debt environments struggle to respond. Systems are brittle, dependencies are tangled, and knowledge is fragmented. What should be a quick patch turns into weeks of testing, rewrites, and risk management – a clear example of the hidden cost of technical debt in action.
Economic impact
Technical debt raises both the likelihood and the cost of security incidents:
- Legacy systems are more vulnerable and significantly harder to secure, while breaches take longer to detect and contain.
- Recovery often requires major rebuilds rather than targeted fixes.
- Compliance gaps emerge as outdated systems fall out of regulatory alignment – fines inevitably follow.
- Prolonged incidents erode customer trust and brand credibility.
- Dependencies stack up, forcing teams to ‘stair-step’ through multiple versions just to reach a secure baseline.
Over time, the cost of inaction piles up. Minor updates deferred today turn into full rewrites tomorrow, dependencies compound, and teams are forced to ‘stair-step’ through multiple versions just to reach a secure baseline. All this explains why organisations that delay reducing technical debt see their remediation costs spiral.
Operational impact
Security debt quietly consumes engineering capacity:
- 40% of developers spend 2-5 days a month on technical debt instead of building new value.
- Fragile systems require constant patching to stay operational.
- Legacy constraints force inefficient workarounds that slow delivery.
- Poorly maintained environments create bugs that shouldn’t exist.
As complexity grows, delivery predictably slows. Even small changes require extensive testing because no one is sure what might break. Teams spend more time putting out fires than building meaningful features, morale drops, and burnout increases. Over time, turnover erodes institutional knowledge, reinforcing the cycle.
Benefits of reducing technical debt
Teams that actively manage technical debt see clear improvements across security, cost, and delivery speed. The benefits of reducing technical debt extend far beyond engineering teams.
Security benefits
Well-maintained systems are harder to exploit. There are fewer gaps for attacks, patches roll out faster, and incident response improves because teams understand how their systems actually work. One of the immediate benefits of reducing technical debt is faster, calmer recovery when something does go wrong.
Business benefits
Reducing technical debt delivers real financial returns. Continuous, small fixes replace rare, expensive overhauls. Breach costs fall as attack surfaces shrink and detection improves. Engineering time shifts from firefighting back to roadmap work.
Reliability improves as systems become more stable and predictable. Compliance is easier to maintain, with fewer exceptions and compensating controls – this makes audits faster and less painful.
| Metric | High technical debt | Managed technical debt |
|---|---|---|
| Risk exposure | Expanding attack surface, slow patching | Shrinking attack surface, faster response |
| Remediation cost | Exponential (rewrites, fire drills) | Linear (small, continuous fixes) |
| Engineering velocity | A large share is lost to debt | The majority focused on roadmap work |
How to manage and reduce technical debt without halting delivery
Understanding how to manage technical debt doesn’t mean stopping all feature work. It means treating debt reduction as a continuous, visible priority.
Governance and communication
Make technical and security debt visible – put it on the roadmap and risk register, not buried in the backlog. Clear visibility is a foundational step in managing technical debt effectively. Use shared cybersecurity metrics like:
- Vulnerability backlog size
- Mean time to remediate (MTTR)
- Percentage of systems on supported versions.
These metrics translate technical risk into business language that leadership can act on.
Day-to-day practices
Build debt management into everyday workflows. Schedule dependency updates, enforce code review standards, run static analysis, and maintain automated tests so refactoring is safe. Setting aside 10-20% of sprint capacity for remediation is a practical way to reduce technical debt without derailing delivery.
Building the business case: Turning security debt into budget
Security leaders often struggle to secure funding for technical debt work because the value isn’t immediately visible. The key is framing debt as financial risk.
How to quantify the risk
Use likelihood-times-impact thinking. If critical vulnerabilities exist in a payment system, estimate the potential breach cost: fines, downtime, customer churn, and recovery effort. Then compare that to the cost of fixing issues now – a concrete way to justify investment to reduce technical debt.
Industry data shows organisations pay an extra 10-20% on projects due to technical debt. Addressing issues earlier – instead of deferring them – significantly lowers the long-term cost of technical debt.
Creating a narrative that resonates with execs
Use the ‘interest versus principal’ metaphor. Every sprint spent working around fragile systems is interest on accumulated debt. Fixing root causes pays down the principal, lowering ongoing costs and freeing capacity for growth. This framing makes managing technical debt intuitive for non-technical leaders.
Where regular pentesting fits in
One-off penetration tests often uncover years of accumulated security debt – outdated libraries, insecure defaults, forgotten systems. The result is a long remediation list, rushed timelines, and unexpected budget requests.
Regular penetration testing changes the equation:
- Large, disruptive fixes are replaced with smaller, ongoing improvements.
- Issues are found earlier, when fixes are cheaper and less disruptive.
- Remediation can be prioritised by real-world exploitability and business impact.
OnSecurity’s penetration testing services help teams continuously surface and prioritise security-relevant technical debt, reduce remediation costs over time, and clearly demonstrate risk reduction to leadership.
Start your pentest quote today and take the first step towards turning technical debt from a hidden liability into a controlled, manageable programme.
