Buffer overflow is one of the oldest and most well-understood vulnerabilities in computing. It's also still responsible for critical CVEs in 2026. Here's why it persists and what it means.
Programs allocate fixed-size buffers in memory. If you write more data than the buffer holds, the excess data overwrites adjacent memory.
// Vulnerable C code
void login(char *username) {
char buffer[64];
strcpy(buffer, username); // No length check!
// If username > 64 bytes, overwrites adjacent memory
}If the adjacent memory contains a function return address, an attacker can redirect execution to their shellcode.
Despite Rust's growth, the world runs on C and C++:
Fixing buffer overflows in existing codebases requires:
This is expensive. Many organizations defer it.
Randomizes memory layout so attackers can't predict where their shellcode will land.
A random value placed before the return address — if it's modified, the program detects the overflow and terminates:
[Buffer][Canary][Return Address]
↑ ↑
Overflow here Overflow must
corrupt canary
first → detected
Mark stack memory as non-executable — shellcode in the buffer can't run.
Modern compilers restrict where jumps can target.
// Rust prevents this class of bug at compile time
fn login(username: &str) {
let mut buffer = [0u8; 64];
// Can't overflow — Rust enforces bounds at compile and runtime
let len = username.len().min(64);
buffer[..len].copy_from_slice(&username.as_bytes()[..len]);
}Rust's memory safety model eliminates the entire class of memory corruption bugs. This is why it's being adopted for security-critical systems.
Most web developers don't write C. But you run software written in C:
Keeping these patched is your buffer overflow defense.