The Quiet Threat of N-Day Vulnerabilities
In the world of Operational Technology (OT), it’s not always the zero-days that pose the biggest threat. Sometimes, they’re the ones we’ve already documented, disclosed, and failed to fix. N-day vulnerabilities, publicly known flaws with available patches are being increasingly weaponized in real-world attacks. Every delay caused by uptime pressures, outdated systems, or poor visibility turns a known vulnerability into a blueprint for compromise. The lesson? It’s not just about discovering new threats, it’s about closing the doors we already know are open. Timely patching isn’t optional; it’s a frontline defence.
The OT Challenge: Why Patching Isn’t So Simple
In IT, patching is fast and repeatable. In OT, it’s slow, siloed, and risky. Critical systems can’t just be rebooted, and attackers know that.
While patching remains essential for securing systems against known vulnerabilities, OT environments present unique challenges that delay or derail timely patch implementation.
Common barriers include:
- Downtime Aversion: Even planned downtime disrupts critical operations and revenues
- OEM Dependency: Many systems can only be patched by vendors or certified integrators
- Siloed Responsibility: IT owns security; OT owns uptime, patching falls in between
- Legacy Constraints: Older systems may break under updates or be incompatible altogether
The Risk of Delay: Known Vulnerabilities with Real Consequences
When organizations delay patching, especially in critical infrastructure and OT environments, the results aren’t just theoretical. They’re disruptive, expensive, and increasingly public.
Recent events across sectors show that attackers aren’t always chasing zero days. More often, they’re exploiting well-documented, unpatched vulnerabilities that have been exposed for weeks, months, or even years.
According to a recent report by the Cyber Management Alliance, the following are some of the most high-profile incidents of 2025 where known, fixable vulnerabilities were left unaddressed and subsequently exploited with serious consequences:
- Commvault CVE-2025-3928 – June 2025
Despite a patch being released rapidly, Commvault’s backup solution was exploited in the wild through a critical vulnerability (CVE-2025-3928). Systems not immediately updated became an open door for attackers
- Ascension Health Breach – May 2025
Ascension, one of the U.S.’s largest health networks, faced a large-scale breach due to unpatched vendor software. The attackers accessed clinical systems and patient data, forcing several hospitals to divert patients and delay treatments
- Synnovis Ransomware Attack – April 2025
The UK-based pathology provider Synnovis, serving multiple NHS Trusts, was crippled by a ransomware attack. Lab systems were taken offline for weeks, disrupting over 1,200 cancer diagnoses and delaying over 2,000 procedures. Investigations linked the breach to unpatched IT infrastructure critical failure in an environment where uptime is vital, but security maintenance lagged
These cases reveal a common thread: the vulnerabilities weren’t new, they were known, documented, and fixable. But delays whether due to operational hesitation, vendor bottlenecks, or lack of visibility turned manageable issues into breach headlines.
From Chaos to Control: A Smarter OT Patch Strategy
Patch management in OT environments isn’t just a best practice it’s a regulatory expectation. While IT systems have matured with automated, repeatable patching processes, OT still struggles with fragmented approaches, manual interventions, and organizational silos. The result? vulnerabilities stay exposed far longer than they should and attackers are capitalizing on that delay.
OT systems need structure, not speed. Effective patching requires:
- Prioritize based on exploitability, exposure, and operational impact
- Schedule patch windows during planned maintenance or shift transitions
- Test in staging before full deployment
- Use frameworks like IEC 62443, NIST SP 800-82
Best Practices for Industrial Patch Management
- Maintain an up-to-date asset inventory
- Track OEM patch notices
- Identify assets with unmitigated critical vulnerabilities
- Automate patch status monitoring wherever possible
- Keep audit-ready logs of patch applications and risk ratings
Final Thought: Known Doesn’t Mean Safe
In OT, resilience doesn’t start with fancy AI or firewalls, it starts with basics done well. Timely patching remains one of the most effective measures against known vulnerabilities. But it requires visibility, prioritization, and coordination across teams.
