The legacy problem in operating systems
Most mainstream operating systems evolved incrementally rather than being redesigned from the ground up. Early systems assumed trusted users, limited connectivity, and benign software environments. Security was not a primary concern because the environment itself was not adversarial.
As operating systems grew and networking became ubiquitous, security mechanisms were layered onto architectures that were never designed for hostile actors. While this approach mitigates individual issues, it creates structural weaknesses that cannot be fully eliminated through patching alone. Major incidents such as the WannaCry ransomware outbreak, which exploited a legacy SMBv1 implementation in Windows to spread rapidly across networks, show how old assumptions about local networks can become large-scale systemic failures when exposed to the internet. 1
These aren't abstract risks. In 2023 alone, kernel-level flaws contributed to breaches costing organizations over $4.5 million per incident on average, with Linux server compromises enabling ransomware spread across cloud fleets and Windows driver exploits powering nation-state persistence. Legacy assumptions don't just create bugs; they turn patches into whack-a-mole and every unpatched system into a potential pivot point.
Specific examples of legacy-driven vulnerabilities
Memory safety failures. A large percentage of critical vulnerabilities involve buffer overflows, use-after-free errors, and heap corruption. These flaws are inherent to unsafe memory handling in low-level system components, particularly those written decades ago in languages that permit unchecked memory access, such as C and C++. 2 Well-known incidents like the Dirty COW vulnerability (CVE-2016-5195), which allowed unprivileged users to modify read-only mappings and escalate to root, and kernel heap overflows used for container escapes show how a single memory bug can reliably become full system compromise. 3
Monolithic kernel assumptions. Many operating systems rely on monolithic kernels in which device drivers and core subsystems execute with elevated privileges. Vulnerabilities in drivers remain a common root cause of full system compromise, because a bug in a single component running in kernel space can immediately escalate an attacker from local code execution to total control.
Backward compatibility pressure. Operating systems preserve outdated APIs, drivers, and execution models to maintain compatibility with legacy software. This perpetuates insecure assumptions long past their original context and significantly expands attack surface. Exploits that target long-deprecated protocols or interfaces, such as SMBv1 in Windows, are one visible manifestation of this pressure to keep old behavior alive for compatibility reasons. 1
These technical issues become far more dangerous when combined with coarse-grained privilege models that allow a single flaw to compromise the entire system.
The superuser problem in Unix-based systems
Perhaps the most consequential legacy security weakness inherited by many modern operating systems is the Unix superuser model, commonly known as root.
In traditional Unix systems, the superuser possesses unrestricted authority over the entire system. This includes adding users, managing devices, modifying system configuration, terminating any process, and bypassing all access controls. This aggregation of power directly violates the Principle of Least Privilege. In many modern breaches, initial access through a misconfigured service or vulnerable daemon becomes catastrophic precisely because it can eventually yield root-level control.
Privilege creep and root as an attack multiplier. In practice, many routine administrative tasks are executed using root privileges because the operating system provides no practical alternative. Simple tasks such as installing printers, managing services, or adding users are often performed as root. Once granted, these privileges allow creation or promotion of additional superuser accounts, turning minor compromises into full system takeovers.
Why root still exists
Over 70% of Linux admin scripts still invoke sudo without bounds checking.
Root persists not because it is ideal, but because it is deeply embedded in Unix compatibility expectations. Thousands of administrative tools, scripts, installers, and workflows assume the existence of a single, all-powerful authority. Removing or fully partitioning root would break decades of software and operational practices. Over time, root has become not just a technical construct but a social and operational convention, embedded in documentation, training, and culture.
Binary privilege models on multi-level hardware
Unix-based operating systems employ a largely binary privilege model: a process is either root or it is not. This persists despite the fact that underlying hardware architectures have supported multiple privilege levels for decades.
On x86 and x86-64 systems, four privilege rings exist, yet most Unix-like operating systems use only Ring 0 for the kernel and Ring 3 for user processes, leaving intermediate rings unused. 4 ARM architectures similarly provide multiple privilege modes, yet Unix-derived systems typically collapse authority into a kernel-versus-user distinction. This was not a hardware limitation. It was a software design choice driven by portability, simplicity, and performance considerations in early Unix systems.
The net effect is that modern systems routinely run 21st-century workloads on privilege architectures largely frozen in 20th-century assumptions.
Linux and legacy code
Linux is widely regarded as robust, well-audited, and rapidly patched. It is the backbone of much of the internet and cloud infrastructure, and its responsiveness to vulnerabilities is exemplary. However, it is also a long-lived codebase originating in the early 1990s. Many Linux vulnerabilities arise in mature subsystems such as file systems, networking stacks, and device drivers. Open development enables transparency and rapid fixes, but does not eliminate architectural inheritance or technical debt.
Rapid patching can limit exposure time but cannot by itself change the underlying reality that a single kernel or driver bug often retains the potential to become a full-system compromise. From the attacker's perspective, techniques such as "bring your own vulnerable driver" on other platforms have direct analogues in Linux, where any kernel-space flaw can be repurposed as a privilege escalation tool.
Linux kernel vulnerabilities and real-world buffer overflows
Linux's position at the heart of servers, cloud platforms, and embedded devices means that kernel vulnerabilities have broad and immediate impact. Because the kernel is largely implemented in C and performance-critical paths favor direct pointer and memory manipulation, memory corruption bugs such as buffer overflows and use-after-free errors remain a recurring class of high-severity issues. 2 When these occur in kernel space, they often provide a direct path to arbitrary code execution with the highest possible privileges.
A prominent example is the "Dirty COW" vulnerability (CVE-2016-5195), a race condition in the Linux kernel's copy-on-write implementation. 3 Dirty COW allowed an unprivileged local user to gain write access to otherwise read-only memory mappings, enabling modification of root-owned files or setuid binaries and escalation to full root control; real-world exploits used this to create new privileged users or inject backdoors on compromised systems.5 More recently, heap-based buffer overflows in kernel subsystems such as the Transparent Inter-Process Communication (TIPC) module (CVE-2021-43267) have demonstrated how an attacker on the same network can remotely trigger out-of-bounds writes in kernel memory and potentially execute arbitrary code in the kernel, turning a single remotely reachable service into a complete host takeover.6
Containerized and cloud workloads further illustrate how kernel buffer overflows undermine higher-level isolation. The CVE-2022-0185 vulnerability in the Linux filesystem context handling introduced a heap-based buffer overflow that allowed unprivileged attackers to escape containers or sandboxes and escalate to root on the underlying host, bypassing namespace restrictions. 7 Other buffer overflow issues in network and virtualization drivers have been shown to leak kernel addresses or enable local privilege escalation, again highlighting that a single bounds-check failure in a widely deployed kernel component can become a reliable primitive for breaking isolation at scale. 2, 8 These cases underscore the central argument of this article: when legacy memory-unsafe code runs in a monolithic, all-powerful kernel, individual bugs routinely become structural compromises rather than contained faults.
OpenBSD and the limits of hardening
Among Unix-like systems, OpenBSD represents one of the most disciplined attempts to make Unix as secure as possible without abandoning its fundamental design. Through proactive auditing, privilege separation, and secure defaults, OpenBSD reduces attack surface significantly.
However, it still operates within inherited Unix constraints: root exists, and a single kernel compromise remains catastrophic. Hardening can reduce the frequency and ease of successful attacks, but it does not change the blast radius when an attacker finally reaches kernel space.
Why Apple systems are generally more secure
Apple platforms experience fewer self-propagating malware incidents largely due to deliberate architectural and policy decisions. Apple tightly controls hardware, firmware, boot chains, and application distribution. Mandatory sandboxing, code signing, and secure boot reduce attack surface and constrain compromise. 9 Apple has also demonstrated a willingness to break backward compatibility, preventing indefinite accumulation of insecure legacy components.
These choices do not make Apple platforms invulnerable, but they do materially reduce certain categories of large-scale compromise. They also illustrate how far hardening and ecosystem control can go without fundamentally replacing inherited privilege and compatibility models. OpenBSD and Apple, in different ways, both show the upper bound of what can be achieved by making existing architectures safer rather than redesigning them.
Microsoft Windows: legacy, compatibility, and administrative power
No discussion of operating system security and legacy design is complete without examining Microsoft Windows. Windows has a long lineage from Windows NT through modern releases, and like Unix-derived systems it carries forward assumptions and components that predate today's threat environment.
Early versions of Windows NT were designed to meet then-current evaluation criteria such as the U.S. government's C2 security rating, focusing on features like secure logon, discretionary access control, and auditing. 10 Over time, Windows evolved into the dominant desktop and enterprise platform, and backward compatibility with older applications, drivers, and protocols became a major design driver. Features such as SMBv1, designed for trusted local networks, persisted for decades, ultimately enabling mass exploitation events such as WannaCry when combined with remotely exploitable vulnerabilities. 1
Windows uses a privilege model centered on accounts and groups, with local administrators and the SYSTEM account possessing very broad authority. In practice, many enterprise tools, installers, and management workflows assume local administrator privileges, mirroring the Unix tendency to use root for routine tasks. Once an attacker attains local administrator rights on a Windows host, widely used tools like Mimikatz can often extract credentials from the LSASS process and use them for lateral movement across the network, illustrating how concentrated authority and credential reuse can turn a single compromise into a domain-wide incident. 11
Kernel-level code remains a critical weak point. Device drivers and other kernel-mode components run with the highest privileges. Techniques such as "bring your own vulnerable driver" (BYOVD) exploit legitimate but vulnerable or mis-signed drivers to gain arbitrary kernel memory access, bypassing protections like Driver Signature Enforcement and Hypervisor-Protected Code Integrity. 12 Once in the kernel, attackers can escalate any process, disable security tooling, or load additional unsigned code, again demonstrating how monolithic trust in kernel-mode code amplifies the impact of individual bugs.
Windows also shows the tension between compatibility and security in stark relief. The need to support older software and drivers has often delayed the deprecation or removal of risky components, from legacy protocols to older authentication mechanisms. Incremental improvements like User Account Control, Protected LSASS, Credential Guard, and virtualization-based security help constrain damage, but they sit atop an architecture where a relatively small number of privileged entities (local admins, SYSTEM, domain controllers, kernel drivers) still represent single points of catastrophic failure when compromised. 11,12
Project Phoenix: compatibility without inherited risk
Project Phoenix is being designed to address these systemic issues by isolating compatibility rather than embedding it into the kernel or primary code of the operating system.
Legacy and modern applications alike will execute in sandboxed environments that strictly mediate access to the kernel, to each other, and to system-wide resources, using explicit, auditable interfaces instead of implicit trust. Think of it as running a zoo where legacy apps are powerful but unpredictable animals: each gets its own secure enclosure with controlled feeding tubes to the outside world, rather than free-roaming access to the entire facility. A lion (legacy x86 app) can roar and perform, but it can't access the elephant's water supply or the zookeeper's keys. Compatibility will be preserved, but trust will not be assumed. The goal is to let existing software continue to run while preventing it from dragging forward the broad, unbounded assumptions that made sense on isolated, trusted networks but are dangerous on today's internet.
Rather than relying on an all-powerful superuser, Project Phoenix is intended to partition administrative authority across narrowly scoped roles and services. In practice, that means distinct authorities for software installation, configuration, and runtime management; time-bounded and scope-bounded elevation for administrative actions; and service-specific permissions that cannot be trivially chained into full-system control. Routine tasks will execute with only the privileges required, preventing simple functions from becoming pathways to total system control.
Phoenix is also designed to align its privilege model with the underlying hardware, making use of multiple privilege levels and isolation mechanisms that most Unix-derived systems and Windows historically leave unused. 4 Instead of collapsing everything into a kernel-versus-user dichotomy, Phoenix treats the hardware's multi-level protection model as a first-class design asset. Microkernels tried similar isolation approaches but struggled with performance; Phoenix learns from them by prioritizing hardware-native mechanisms over software emulation.
Regulatory direction and the future
The European Union's Cyber Resilience Act mandates security-by-design, vulnerability handling, and lifecycle responsibility for digital products. It emphasizes secure defaults, secure boot, access controls, and mechanisms such as sandboxing and privilege separation to prevent lateral movement and unauthorized access. 9,13 The United States currently relies on a fragmented enforcement and liability-based approach, but regulatory trends increasingly treat insecure software as a systemic risk rather than a user failure.
Operating systems architected to contain legacy risk, enforce isolation, and support long-term security maintenance are better positioned for this emerging environment. As regulators increasingly expect demonstrable security properties such as constrained blast radius, clear isolation boundaries, and robust update mechanisms, architectures that treat these as core design goals rather than add-ons will have a structural advantage.
Conclusion
Most operating system vulnerabilities exist not because of modern engineering failures, but because systems outlived the assumptions they were built upon. Security cannot be retrofitted indefinitely.
The future of operating system security lies in treating compatibility as managed risk, enforcing isolation by default, partitioning authority, and aligning software trust models with hardware capabilities. Project Phoenix doesn't bet on perfect software. It bets on architecture that survives imperfection. It will not attempt to erase the past. Instead, it will contain it, allowing legacy and modern software to run without permitting inherited assumptions to define the security of the system.
Notes
1 SMB Exploited: WannaCry Use of "EternalBlue" and Malware.news analysis
2 TuxCare: Memory Corruption Vulnerabilities in the Linux Kernel and LinuxSecurity: Buffer Overflow Risks
3 Red Hat: Dirty COW CVE-2016-5195 and SecPod: Dirty COW Vulnerability
4 Windows NT Security, Part 1 (historical context for privilege rings)
5 4Geeks: Dirty Cow Kernel Exploit
6 SentinelOne: CVE-2021-43267 TIPC Heap Overflow
7 CrowdStrike: CVE-2022-0185 Kubernetes Escape and HackTheBox Case Study
8 CVE Details: CVE-2019-14896 Heap Buffer Overflow
9 IAPP: EU Cyber Resilience Act 101 (Apple security context)
10 ITPro Today: Windows NT Security Part 1
11 SOC Prime: Hunting Malicious LSASS Access and SideChannel: Mimikatz Mitigation
12 SC Media: Windows Kernel Attacks via Signed Drivers and Cisco Talos: Vulnerable Windows Drivers