
The Rust Security Myth: Why Migrating from C++ Wont Solve Your Security Problems
The Rust Security Myth: Why Migrating from C++ Wonât Solve Your Security Problems
If youâve been anywhere near tech Twitter, LinkedIn, or programming forums lately, youâve probably seen the breathless posts: âRust is the future of systems programmingâ or âC++ is fundamentally unsafe - rewrite it all in Rust!â My LinkedIn feed has become a parade of academic researchers and self-styled thought leaders declaring the death of C++, each post garnering thousands of likes from people whoâve never had to maintain a million-line codebase in production.
Itâs the kind of hype cycle weâve seen before, where a genuine technical advancement gets transformed into a silver bullet that will supposedly solve all our problems. The academic crowd is particularly enthusiastic, publishing papers that compare the theoretical safety guarantees while conveniently ignoring the practical challenges of real-world software development.
Iâve been thinking about this lately not because Iâm convinced by the hype, but because Iâm troubled by how it distorts engineering decisions. The pressure to adopt Rust isnât coming from careful technical evaluation - itâs coming from the same kind of groupthink that once declared that all serious applications should be written in Java, or that NoSQL would make traditional databases obsolete. Itâs amplified by an echo chamber of LinkedIn influencers who seem more interested in riding the wave of the next big thing than in the nuanced reality of engineering trade-offs.
What makes this particular hype cycle frustrating is how itâs built around a carefully constructed narrative about memory safety that doesnât hold up to scrutiny. Yes, Rust has a strict ownership model and compile-time checks. But the idea that this represents some revolutionary breakthrough in safety is more marketing than reality. Ada had similar safety guarantees decades ago. Modern C++ with proper tooling and static analysis can achieve comparable safety levels. The leap from âRust enforces certain patterns at compile-timeâ to âyou should rewrite your C++ codebase in Rustâ reveals more about our industryâs susceptibility to marketing than any fundamental breakthrough in software engineering.
The memory safety argument starts to fall apart when you look at real-world systems. Most critical vulnerabilities in mature C++ codebases donât come from raw pointer misuse - they come from design flaws, logic errors, and integration issues that no amount of compile-time checking will catch. The Rust evangelists conveniently ignore this reality, focusing instead on theoretical memory safety while dismissing decades of battle-tested C++ patterns and tools.
The interesting thing about the security argument for Rust is that itâs both completely true and somewhat misleading. Rust is indeed more secure than C++ by design. Its ownership model and borrow checker prevent entire categories of memory safety bugs at compile time. This is genuine progress in programming language design.
But thereâs a leap of logic that happens next. People assume that because Rust is more secure by design, rewriting your C++ codebase in Rust will make your software more secure. This seems like it should be true, but reality is messier.
Consider what actually happens when a large organization decides to rewrite their C++ codebase in Rust. First, you have to train your engineers. Even excellent C++ programmers need months to become proficient in Rust. During this time, theyâre more likely to make mistakes - not just in Rust, but in working with the existing C++ code as their mental models shift.
One of the most persistent myths in the Rust advocacy narrative is that C++ lacks modern ownership and borrowing capabilities. This claim reveals either a concerning ignorance of modern C++ or a deliberate misrepresentation of its features. Modern C++ provides robust ownership and borrowing mechanisms that offer similar safety guarantees to Rust, but with the added benefit of flexibility in their application.
Consider how C++ handles exclusive ownership through std::unique_ptr. This smart pointer type implements move semantics that enforce single ownership at compile time - when you transfer ownership, the original pointer becomes null, preventing use-after-move errors just as effectively as Rustâs ownership system. The key difference is that C++ allows you to choose when to apply these constraints, rather than forcing them universally.
C++âs borrowing mechanisms are equally sophisticated. References provide temporary access to resources without transferring ownership, while the newer std::span offers safe array and container access with bounds checking. These arenât mere afterthoughts - theyâre core features that enable safe resource management in large-scale systems. The introduction of [[ensures_borrowed]] attributes in C++26 even adds compile-time borrowing verification, directly challenging the notion that only Rust can provide such guarantees.
For scenarios requiring shared ownership, C++ offers std::shared_ptr and std::weak_ptr, providing reference-counted ownership with cycle detection capabilities. Letâs look at a real-world example similar to what desktop environments like COSMIC face - a window management system where windows can contain child windows, but child windows also need to reference their parents for event propagation:
class Window {
std::string name;
// Strong ownership of child windows
std::vector<std::shared_ptr<Window>> children;
// Weak reference to parent to prevent cycles
std::weak_ptr<Window> parent;
public:
explicit Window(std::string n) : name(std::move(n)) {}
void add_child(std::shared_ptr<Window> child) {
// Set up parent-child relationship without creating cycles
children.push_back(child);
child->parent = std::weak_ptr<Window>(children.back());
}
void propagate_event(const Event& evt) {
// Safe access to parent even if it's been destroyed
if (auto p = parent.lock()) {
p->handle_event(evt);
}
// Children are guaranteed to exist due to strong ownership
for (const auto& child : children) {
child->handle_event(evt);
}
}
};
Perhaps the most troubling aspect of the current Rust advocacy is how often technical decisions are being influenced by what can only be described as technological fashion. In numerous technical discussions and architecture meetings, weâre increasingly hearing variations of âRust is the cool new thingâ presented as a legitimate argument for system rewrites. This represents a concerning shift in engineering decision-making from objective analysis to social signaling.
The phenomenon manifests in several ways. Job postings prominently feature Rust as a way to appear cutting-edge, regardless of whether itâs the optimal tool for their systems. Conference talks and technical blogs disproportionately focus on Rust, not because it solves problems better than existing solutions, but because it generates more social media engagement. Even technical architects, who should know better, sometimes advocate for Rust adoption primarily to make their organizations appear more attractive to potential hires.
This âcoolness-driven developmentâ is particularly dangerous because it masquerades as technical progressiveness while actually representing a regression in engineering rigor. When we examine successful, large-scale systems that have stood the test of time, we find they were built on careful technical evaluation, not technological fashion. The Linux kernel, which powers most of the worldâs servers, continues to be primarily written in C. Major financial systems handling trillions of dollars in transactions remain implemented in C++. These arenât signs of technological stagnation - theyâre evidence of engineering maturity that prioritizes proven reliability over trending technologies.
The argument that âRust is coolâ also reveals a deeper misunderstanding about professional software engineering. In a mature engineering discipline, we select tools based on their fitness for purpose, not their position in the hype cycle. When civil engineers choose materials for a bridge, they donât base their decision on which material is currently trending on engineering Twitter. Yet somehow, in software engineering, weâve normalized making architectural decisions based on what will look impressive on a resume or generate the most LinkedIn engagement.
The flexibility of C++âs approach becomes particularly valuable when we examine how companies actually modernize their codebases. Rather than forcing a complete rewrite, teams can gradually adopt these safety patterns where they provide the most benefit. This pragmatic approach acknowledges a truth that Rust evangelists often overlook: the biggest security risks in mature systems rarely come from raw pointer misuse, but from architectural decisions and integration patterns that no amount of compile-time checking can fully address. The danger isnât just in introducing new bugs (though that will happen). The real risk is in the invisible knowledge embedded in the old code - the edge cases and corner cases discovered and handled over years of production use.
But letâs say you navigate these challenges successfully. You still have to maintain backward compatibility, which usually means keeping some C++ code around and creating FFI boundaries between C++ and Rust. These boundaries are often where security vulnerabilities hide.
The irony is that modern C++ already provides most of the tools you need for memory safety. C++26 introduces bounded arrays with compile-time checks, ownership annotations that approach Rustâs guarantees, and safe integer operations that prevent overflow vulnerabilities. Hereâs what that looks like:
std::bounded_array<int, 5> safe_array{1, 2, 3, 4, 5};
[[ensures_owned]] void process_resource(std::unique_ptr<Resource>&& resource);
std::safe<int> value = std::numeric_limits<int>::max();
The difference is that C++ makes these features optional, while Rust makes them mandatory. This is both C++âs weakness and its strength. Itâs a weakness because programmers can ignore these features. But itâs a strength because it allows for gradual adoption and pragmatic tradeoffs.
I think thereâs a broader lesson here about how technology adoption really works. We tend to imagine it as a series of clean breaks - from assembly to C, from C to C++, from C++ to Rust. But successful technology adoption usually looks more like sedimentary rock, with new layers building on top of old ones rather than replacing them entirely.
The most successful transitions Iâve seen follow a pattern: start by adopting modern practices in your current technology, then introduce the new technology at the edges where it makes the most sense. For C++ codebases, this means first moving to modern C++ idioms, using smart pointers, implementing bounds checking, and leveraging static analysis tools.
Once youâve done that, you might find that Rust makes sense for certain new components - perhaps a security-critical parser or a new microservice. This gradual approach lets you learn and adapt while maintaining velocity. Itâs less exciting than a grand rewrite, but itâs more likely to succeed.
Thereâs a tendency in our industry to focus on technical features while underestimating organizational factors. Yes, Rustâs memory safety guarantees are superior to C++âs. But the security of your software depends more on your teamâs expertise, your testing practices, and your deployment processes than on your choice of programming language.
The teams Iâve seen achieve the best security outcomes arenât necessarily the ones using the most secure languages. Theyâre the ones with a culture of security awareness, good code review practices, comprehensive testing, and continuous learning.
This doesnât mean Rust is the wrong choice. For new projects, especially in security-critical domains, Rust is often the right choice, depending on the assessment. Its guaranteed memory safety is valuable, and you donât have to pay the cost of migration. But for existing C++ codebases, the calculation is different.
Still considering new projects in C++? Yeah, thatâs reasonable. C++ is a mature language with a vast ecosystem, and modern C++ practices can be surprisingly safe. And it is evolving, even if the bias talks a different language. But if do not care about bias and emotions, but about rational aspects and youâre thinking about rewriting your entire C++ codebase in Rust for security reasons, you might want to pause and consider the broader context.
The real challenge isnât choosing between C++ and Rust and thus current discussion variations are misleading. The challenge is about building secure software in an imperfect world. That requires balancing technical features against organizational constraints, immediate gains against long-term maintenance costs, and ideal solutions against practical realities.
If youâre wrestling with this decision, Iâd suggest asking different questions. Instead of âShould we rewrite in Rust?â, ask âHow can we most effectively improve our softwareâs security given our constraints?â The answer might involve Rust, but it might also involve better tooling, improved processes, or more training in modern C++ practices.
The future probably isnât a wholesale replacement of C++ with Rust. Itâs more likely a gradual evolution where both languages coexist, each used where it makes the most sense. Thatâs less satisfying than a clear winner-takes-all narrative, but itâs probably closer to reality.
Technical problems often have clean, elegant solutions. Organizational problems rarely do. The challenge of securing existing software is as much organizational as technical. The sooner we recognize that, the better our solutions will be.