The Rust Security Myth: Why Migrating from C++ Won’t Solve Your Security Problems

If you’ve been anywhere near tech Twitter, LinkedIn, or programming forums lately, you’ve probably seen the breathless posts: “Rust is the future of systems programming” or “C++ is fundamentally unsafe - rewrite it all in Rust!” 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 who’ve never had to maintain a million-line codebase in production.

It’s the kind of hype cycle we’ve 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.

I’ve been thinking about this lately not because I’m convinced by the hype, but because I’m troubled by how it distorts engineering decisions. The pressure to adopt Rust isn’t coming from careful technical evaluation - it’s 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. It’s 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 it’s built around a carefully constructed narrative about memory safety that doesn’t 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 “Rust enforces certain patterns at compile-time” to “you should rewrite your C++ codebase in Rust” reveals more about our industry’s 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 don’t 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 it’s 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 there’s 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, they’re 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 Rust’s ownership system. The key difference is that C++ allows you to choose when to apply these constraints, rather than forcing them universally.

C++‘s 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 aren’t mere afterthoughts - they’re 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. Let’s 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, we’re increasingly hearing variations of “Rust is the cool new thing” 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 it’s 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 “coolness-driven development” 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 world’s servers, continues to be primarily written in C. Major financial systems handling trillions of dollars in transactions remain implemented in C++. These aren’t signs of technological stagnation - they’re evidence of engineering maturity that prioritizes proven reliability over trending technologies.

The argument that “Rust is cool” 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 don’t base their decision on which material is currently trending on engineering Twitter. Yet somehow, in software engineering, we’ve normalized making architectural decisions based on what will look impressive on a resume or generate the most LinkedIn engagement.

The flexibility of C++‘s 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 isn’t 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 let’s 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 Rust’s guarantees, and safe integer operations that prevent overflow vulnerabilities. Here’s 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++‘s weakness and its strength. It’s a weakness because programmers can ignore these features. But it’s a strength because it allows for gradual adoption and pragmatic tradeoffs.

I think there’s 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 I’ve 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 you’ve 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. It’s less exciting than a grand rewrite, but it’s more likely to succeed.

There’s a tendency in our industry to focus on technical features while underestimating organizational factors. Yes, Rust’s memory safety guarantees are superior to C++‘s. But the security of your software depends more on your team’s expertise, your testing practices, and your deployment processes than on your choice of programming language.

The teams I’ve seen achieve the best security outcomes aren’t necessarily the ones using the most secure languages. They’re the ones with a culture of security awareness, good code review practices, comprehensive testing, and continuous learning.

This doesn’t 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 don’t have to pay the cost of migration. But for existing C++ codebases, the calculation is different.

Still considering new projects in C++? Yeah, that’s 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 you’re 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 isn’t 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 you’re wrestling with this decision, I’d suggest asking different questions. Instead of “Should we rewrite in Rust?”, ask “How can we most effectively improve our software’s security given our constraints?” The answer might involve Rust, but it might also involve better tooling, improved processes, or more training in modern C++ practices.

The future probably isn’t a wholesale replacement of C++ with Rust. It’s more likely a gradual evolution where both languages coexist, each used where it makes the most sense. That’s less satisfying than a clear winner-takes-all narrative, but it’s 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.