Risks of legacy systems in 2026: security, compliance and what to do now

Most businesses that still run outdated software know about the risks of legacy systems. But those systems often sit at the heart of their core processes. They’ve been there for years, the team knows how they work, and changing them seems like more trouble than leaving them alone.

Yet that logic holds only as long as the risks stay the same — and they don’t. Every year outdated software stays in place, it falls further behind business, security and compliance requirements. In 2026, those accumulated legacy system risks are becoming increasingly difficult to justify or ignore.

What counts as a legacy system in 2026?

A legacy system is software that has become difficult to maintain, secure, or adapt to what the business, regulators, or the market now demand. This means age alone doesn’t make a system legacy. A 20-year-old application that’s still supported may be fine, while a five-year-old platform that can’t meet current security standards may already qualify as legacy.

Overall, the key signs that a system may be legacy include:

• Unsupported technology. The software runs on operating systems, frameworks, or databases that no longer receive updates. Example: an application running on .NET 6 that has reached end of support.
• Scarce expertise. Few developers understand the code, documentation is missing, or specialists are hard to find. Example: a VB6 application, a technology that Microsoft stopped developing years ago and that new developers rarely learn.
• Outdated infrastructure. The software depends on aging hardware or components that are hard to replace or upgrade. Example: a system tied to a physical server running Windows Server 2008.
• Security limitations. The software has known vulnerabilities or can’t support modern security measures. Example: a hospital’s patient management system that still uses TLS 1.0 to transmit sensitive data and doesn’t have multi-factor authentication. 
• Risky dependencies. The application relies on outdated libraries, third-party tools, or other systems that introduce additional risk. Example: an ordering app built around nightly exports from a legacy inventory system. 
• Difficulty meeting business needs. Adding features, integrating modern tools, or scaling takes too much time, money, or effort. Example: a desktop-only accounting system that can’t integrate with modern ERP and CRM. 

A system doesn’t need to show every sign. Even one significant risk can be enough to make it legacy.

Why legacy system risks are higher in 2026

Legacy software hasn’t become more dangerous simply because another year has passed. What has changed in 2026 is the environment businesses operate in.

Attackers are focusing on system vulnerabilities 

For years, the easiest way into a company was through its people: a convincing phishing email or a reused password. But last year, the situation changed. According to Verizon’s 2026 Data Breach Investigations Report, exploiting software vulnerabilities is now behind 31% of breaches, up from 20% a year earlier.

For businesses running outdated software, this is particularly concerning. You can train employees to spot phishing, but you can’t fix vulnerabilities in a framework or library that no one maintains anymore. When the technology behind an application stops receiving security updates, every new flaw found in it stays open. 

Popular technologies are reaching EOL

Every year, another set of technologies that businesses, and enterprises in particular, rely on stops receiving security updates and technical support. 2026 has been especially busy, with several widely used technologies either reaching end of life or approaching this point:

• Node.js 20 — April 30, 2026
• SQL Server 2016 — July 14, 2026
• SharePoint Server 2016 and 2019 — July 14, 2026
• Python 3.10 — October 1, 2026
• Office LTSC 2021 — October 13, 2026
• Windows Server 2012 and 2012 R2 — October 13, 2026 (end of the third and final year of Extended Security Updates)
• .NET 8 and .NET 9 — November 10, 2026
• PHP 8.2 — December 31, 2026

A system doesn’t stop working when the technology behind it loses support. The problem is that newly discovered vulnerabilities no longer get fixed. The application keeps running but becomes steadily more exposed to security risks of outdated software. Without an upgrade, you have fewer and fewer ways to keep it protected.

AI is making cyberattacks easier

AI-powered attacks are on the rise. AI makes it easier and cheaper to exploit existing weaknesses in systems, and it helps bad actors build more sophisticated attacks. According to IBM’s 2026 Cost of a Data Breach Report, AI was involved in a quarter of malicious breaches, 56% more than the year before. 

In legacy software, vulnerabilities are often easier to find. Even custom-built systems usually run on outdated frameworks, libraries, or servers with publicly known weaknesses, and AI tools help attackers identify and exploit them faster. Older systems are also less able to defend themselves: many can’t support modern protections such as multi-factor authentication or behavior-based threat detection.

Regulations are becoming stricter 

Cybersecurity and data protection requirements are tightening, especially in regulated industries. Several EU regulations are now raising expectations for how businesses protect their systems and data:

• NIS2 Directive. NIS2 brings far more companies under EU cybersecurity rules, expanding the scope from 7 sectors to 18. Companies that fail to meet its security requirements can be fined up to €10 million or 2% of global turnover, whichever is higher, and management can be held personally liable. 
• Cyber Resilience Act. The CRA sets cybersecurity requirements for software and connected devices sold in the EU. Since September 11, 2026, manufacturers must report actively exploited vulnerabilities within 24 hours, even for older products already on the market. 
• Digital Operational Resilience Act. Applicable from January 2025, DORA requires covered financial organizations in the EU to strengthen IT security, manage third-party risks, and prepare for cyber incidents and operational disruptions.

In the US, the picture is more mixed, but the direction is similar. In healthcare, for example, HHS has proposed the first major update to the HIPAA Security Rule in over a decade, with requirements such as mandatory multi-factor authentication and encryption. 

For organizations that keep putting off modernization, this creates growing legacy system compliance risks as the gap between what their outdated software can do and what the law requires keeps getting wider. 

Security risks of outdated software

According to HFS Research’s 2025, 27% of 305 surveyed enterprise decision-makers ranked security vulnerabilities among the top three consequences of outdated technology. These concerns are well-founded: outdated software often has weaknesses that are difficult to fix. 

The main legacy system security risks include: 

• Unpatched vulnerabilities. When vendors stop releasing security updates, known flaws remain open to exploitation. CISA’s Vulnerability Review, published in August 2026, lists poor patching and outdated, unsupported technology among the main causes of security breaches. 
• Weak authentication and access control. Many older systems can’t support multi-factor authentication or role-based access control. A single stolen password can be enough to get in. 
• Outdated encryption. Legacy software often relies on old encryption standards or protocols, or stores data without encryption at all. This makes it easier for attackers to intercept data in transit or to read stored data once they get into the system. 
• Limited security monitoring. Legacy systems often lack detailed logging and can’t connect to modern monitoring tools, so suspicious activity often goes unnoticed. 
• Unreliable dependencies and integrations. Outdated libraries, frameworks, and connectors can expose systems that are otherwise up to date. 

There’s also a less obvious risk that’s easy to overlook: shrinking expertise. As fewer specialists know older technologies, securing legacy systems becomes harder, with issues taking longer to spot and fix. As a result, some vulnerabilities stay open simply because no one on the team knows how to deal with them without risking the system’s stability. 

Compliance risks of legacy systems 

Compliance is another major area of legacy system risk. An application can work perfectly for employees and customers and still cause problems during an external audit or regulatory investigation. Below are the most common compliance risks of legacy systems. 

Missing audit trails

Legacy systems may not record who accessed, changed, or deleted sensitive information, which in some cases can be a compliance violation. 

Example: if a hospital’s patient management system doesn’t track which employees viewed patient records, it might be difficult to prove alignment with HIPAA compliance standards. 

Poor data deletion controls

Outdated systems can make it hard to find or remove personal data when a customer asks or the law requires it. 

Example: if a company deletes a customer’s information from its CRM but copies remain in an old billing database, it may be breaching the GDPR’s right to erasure. 

Incomplete compliance documentation

Software inventories and patch records for legacy systems are often outdated or missing, which makes audits harder to pass. 

Example: if a bank can’t provide auditors with an accurate inventory of the applications that process customer data, it may fail to meet DORA’s documentation requirements.

Difficulty meeting industry requirements

Some industry standards require controls that legacy software simply can’t support without additional security measures. 

Example: if an online store processes card payments using unsupported software, newly discovered vulnerabilities may remain unpatched, making it difficult to meet PCI DSS requirements.

Unreliable backup and recovery

Older systems may rely on untested backups or infrastructure that is difficult to restore. 

Example: if a bank can’t show that its legacy transaction system can be restored within its own recovery time objectives, it may fail to meet DORA’s business continuity requirements.

These are only the most common examples. Requirements vary by country, industry, and type of data, so it’s worth checking which rules apply to your business and where your legacy systems fall short. 

The business cost of keeping legacy systems

If a business decides to accept the risks of legacy systems, it should understand what that decision may cost, and not just in terms of money. 

Growing maintenance costs 

In HFS Research’s 2025 survey, 42% of enterprise decision-makers named higher maintenance costs among the top three impacts of legacy technology. These costs go beyond routine upkeep. Businesses may need specialized developers, custom fixes, and extra testing whenever something changes, so even small software updates become slow and costly. 

The amount varies widely, but for large enterprises the cost of maintaining legacy systems can be substantial. Pega’s 2025 research puts it at about $56 million a year for the average global enterprise, including updates and integrations. 

Limited innovation and scaling

Keeping legacy systems running can leave you with less money to invest in new technologies and business growth. In the KPMG 2026 Annual US Technology Survey, 56% of US organizations said the cost of dealing with technical debt is holding them back from investing in new technology programs. 

But money isn’t the only problem. Legacy systems often don’t work easily with modern tools: they may lack APIs, use outdated data formats, or be unable to handle more users and data as the business grows. As a result, adopting AI, launching a new digital service, or entering a new market can take far longer than planned, or not happen at all.  

Reduced employee productivity 

Legacy systems also eat into employees’ time. In KPMG’s 2025 survey of technology sector professionals, 55% of respondents said their engineering teams spent 20–40% of their time over the past year fixing technical debt.

But the risks associated with human resources reach beyond IT. In a 2026 Pega survey, 64% of working adults in the US and UK said their workplace tools or systems slow them down or hurt their productivity. Poor technology can also affect retention: 36% would consider leaving their job if their employer doesn’t meet their technology needs.

Operational disruptions 

Another major risk of legacy systems is the operational disruption they can cause, especially when they handle critical business workflows. Even a short outage can interrupt orders, payments, production, or customer service. In the KPMG 2026 Annual US Technology Survey, 40% of US firms said legacy systems still cause them weekly IT glitches.

Recovering from a legacy system failure can also take longer. Missing documentation, outdated infrastructure, and a shortage of specialists may delay repairs and restoration.

Warning signs your legacy system is now a liability (checklist)

Only a professional assessment can show the exact state of your software system. But you don’t need to be a developer to spot signs that something may be wrong. Use this checklist to see whether it’s time to take your legacy IT system risks more seriously. 

1. The system goes down or freezes more often than it used to.
2. Fixing even small issues takes days or weeks.
3. Your team avoids making changes because something else might break.
4. You postpone new features because of the system’s architectural limitations, scalability issues, or integration constraints.
5. IT bills keep growing year after year.
6. Connecting a new system (CRM, payment service, cloud platform, etc.) turns into a costly development project.
7. Employees rely on spreadsheets, manual data entry, or other workarounds to get their work done.
8. Customers complain about slow service, errors, or outdated digital experiences.
9. It’s getting harder to find or keep people who can maintain the system.
10. Auditors, regulators, or insurers have started asking questions about your software.
11. Your security team keeps flagging it as a risk, or it has already been involved in an incident.
12. You turn down opportunities, and new projects get delayed or canceled because the system can’t support them.

You don’t need to check every box to have a problem. If several of these signs sound familiar, it’s worth assessing the system before the next failure forces your hand.

How to mitigate legacy system risks

Modernizing or replacing a legacy system takes time, and in the meantime, it still has to run safely. Below are practical steps you can take to identify the weaknesses that can be fixed and reduce the immediate risks. 

Step 1. Assess your systems 

You can’t manage legacy system risks you don’t know about. So the first step is to build a complete inventory of your applications, infrastructure, and dependencies. Look beyond the software itself to the architecture, frameworks, libraries, and integrations it relies on, since any of these can be a weak point.

Next, check each item for problems:

• Does the vendor or open-source community still provide security updates?
• Are there known vulnerabilities in the versions you’re using?
• Does the system support modern security controls, such as MFA, strong encryption, and detailed activity logs, either directly or through external tools?
• Does it meet the regulations and standards that apply to your business?
• Is the system documented, and does your team have the expertise to maintain it?
• Have backups been tested, and do you know how long recovery would take after a failure?

 This turns your inventory into a list of risks. 

Step 2. Prioritize legacy system risks

Once you’ve identified the risks of legacy systems, prioritize them by how likely they are to cause problems and how severely they could affect your business. These questions about the system where each risk sits can help:

• How critical is the system? Which business processes depend on it?
• How exposed is it? Is it accessible from the internet or connected to other key systems?
• What data does it handle? Does it process personal, financial, or health data?

For example, an unpatched system that handles customer data would normally take priority over a minor performance issue.

The result should be a list of risks ranked by priority, so you know what to address first.

Step 3. Apply available security fixes

Even when the core application is outdated, many of the components around it may still receive updates. Start with the high-priority risks from Step 2 and fix what can be fixed:

• Apply available security patches to supported operating systems, databases, frameworks, libraries, and server software.
• Upgrade outdated dependencies to supported versions where compatible. Sometimes, even a minor version upgrade can fix known vulnerabilities.

It’s important to test updates before deploying them to avoid disrupting critical business functions.

Also, document any issues you can’t resolve immediately. You’ll need this information later.

Step 4. Protect your data 

If a legacy system can’t be fully secured right away, the next best thing is to reduce what an attacker could take from it:

• Delete old records, test data, and personal information the system no longer needs, or move them to a secure archive.
• Limit access to sensitive data to people who actually need it.
• Back up critical data regularly and keep copies in a separate, secure location.

These measures won’t eliminate the underlying legacy software vulnerabilities. But they can reduce the impact of a breach or system failure while you work on longer-term improvements.

Step 5. Test recovery 

Having backups doesn’t mean you can recover from a failure. Legacy systems are often hard to restore. To make sure your recovery plan actually works:

• Simulate a system failure in a safe, isolated environment.
• Run a full restore test of the application, its data, and critical dependencies.
• Measure recovery time and check whether your business can afford to be offline that long.
• Document the process so your team can repeat it when a real failure occurs.

If the test shows that recovery takes too long or doesn’t work at all, that’s another sign the system might need more than maintenance.

Modernize, contain or retire: choosing a path

Mitigation measures can reduce immediate risks and buy time, but they won’t necessarily solve the underlying problems. Once you understand your legacy system risks, you need to decide what to do with the system in the long run. In most cases, that means choosing one of three paths: modernize, contain, or retire. 

Modernize

Legacy system modernization fits software that is still valuable to the business but technically outdated. The goal is to preserve the functionality while updating the technology behind it. 

The right modernization strategy depends on the system’s condition and your goals. Key options include: 

• Rehost — migrating legacy systems to new infrastructure. Example: moving an on-premises ERP from aging servers to cloud-based virtual machines. 
• Replatform — moving the application to a newer platform. Example: migrating a self-managed database to a managed cloud database service. 
• Refactor  — restructuring existing code to improve its quality and maintainability without changing its functionality. Example: improving the code of a legacy .NET billing module to separate invoice calculations from database access and remove duplicated logic. 
• Rearchitect — redesigning how the system is built to make it more flexible and scalable. Example: splitting a large monolithic application into independently deployable microservices.
• Rebuild — rewriting the entire application or selected components using modern technologies. Example: rebuilding a VB6 desktop application as a web application.

Contain

Containment means keeping the legacy system running without major changes to its code, while adding security measures around it. This is done through compensating controls, such as:

• Network segmentation — placing the system in a separate part of the network, so attackers can’t easily move from it to other systems.
• Restricted access — allowing connections only from the users, devices, and systems that actually need them.
• External MFA — requiring multi-factor authentication at the entry point, such as a VPN or secure gateway, if the system can’t support it itself.
• Virtual patching — blocking known attacks before they reach the system, for example with a web application firewall.
• Extra monitoring — setting up alerts for unusual activity.

Containment works best when a system is critical but can’t be modernized or replaced yet, or when the cost of doing so isn’t justified.

Retire

Retirement is shutting down a legacy system that is no longer needed. This may happen when few or no people use the system or another existing system can take over its functions.

But retiring a system isn’t just switching it off. To do it safely, you need to:

• Check dependencies to make sure no other systems rely on it.
• Complete data migration. Move the data you still need to another system, archive records you’re required to keep, and securely delete the rest.
• Clean up access by removing user accounts and connections to other systems.
• Shut down or wipe the servers and storage it ran on, so forgotten copies don’t become a security risk later.

Different pieces of software often need different paths. For example, you might retire an unused reporting module, modernize your legacy customer-facing part, and temporarily contain the core database. 

How we can help

Keeping outdated software running isn’t always the wrong decision. Neither is replacing it. What matters is understanding the legacy system risks, the cost of addressing them, and which approach makes the most sense for your business.

That’s where we can step. Our experienced engineers can assess your system, weigh the options objectively, and plan changes without disrupting the business. 

Explore our legacy software modernization services and discuss your system with our experts.