Security of Rust Applications: Top 10 Vulnerabilities

Introduction: Myths and Reality of Rust Safety

The Rust language is often called "safe" and "reliable," and this is largely true. Thanks to its ownership system and strict compiler, Rust eliminates entire classes of vulnerabilities common in C and C++ (e.g., buffer overflows or dangling pointers). However, this does not mean that Rust applications are invulnerable. In practice, developers encounter logic errors, incorrect use of unsafe, and vulnerabilities at the architecture level.

In this article, we will break down the top 10 most common vulnerabilities in Rust applications. You will learn how they arise, how to detect them, and how to protect your code. The material will be useful for both beginners and experienced developers.

1. Errors in unsafe Code

The most famous "Achilles' heel" of Rust is unsafe blocks. They allow operations that the compiler cannot verify: dereferencing raw pointers, calling external functions (FFI), modifying static variables. If an error is made in unsafe, all of Rust's safety crumbles.

Vulnerability Example

fn unsafe_deref(ptr: *const i32) -> i32 {    unsafe { *ptr } // If ptr is null or points to freed memory — UB}

How to Protect Yourself

• Minimize the use of unsafe. Isolate it into small, thoroughly tested modules.
• Use #[deny(unsafe_code)] in crates where possible.
• Check pointers for validity before dereferencing.

2. Data Races in Multithreaded Code

Rust guarantees the absence of data races in safe code thanks to its ownership and borrowing rules. However, when using unsafe or incorrectly working with Mutex/RwLock, races are possible. Situations with Cell/RefCell in a multithreaded environment are especially dangerous.

Vulnerability Example

use std::cell::RefCell;use std::thread;

fn main() {    let data = RefCell::new(0);    thread::spawn(move || {        *data.borrow_mut() += 1; // Panic: RefCell is not Sync    });}

How to Protect Yourself

• Use Arc<Mutex<T>> or Arc<RwLock<T>> for shared data.
• Avoid unsafe when working with threads unless absolutely necessary.
• Apply the static analyzer clippy and miri to detect undefined behavior.

3. Memory Leaks

Although Rust prevents leaks in most cases, they are still possible. For example, when creating circular references with Rc/RefCell or when forgetting to call a destructor in unsafe code. Memory leaks in long-running services can lead to resource exhaustion.

Vulnerability Example

use std::rc::Rc;use std::cell::RefCell;

struct Node {    next: Option<Rc<RefCell<Node>>>,}

fn main() {    let a = Rc::new(RefCell::new(Node { next: None }));    let b = Rc::new(RefCell::new(Node { next: Some(a.clone()) }));    a.borrow_mut().next = Some(b); // Circular reference — leak}

How to Protect Yourself

• Use Weak to break circular references.
• For long-running applications, use memory profilers (e.g., valgrind or heaptrack).
• In unsafe code, always verify that memory is freed correctly.

4. Incorrect Error Handling

Rust encourages explicit error handling through Result and Option. However, developers often ignore errors by using .unwrap() or .expect(). In production, this can lead to p