CVE-2020–19186: Unmasking the Buffer Overflow Beast

In the vast realm of cybersecurity, vulnerabilities lurk like shadows. One such shadowy figure is CVE-2020–19186, a buffer overflow vulnerability that haunts the code of ncurses 6.1. But fear not! In this article, we’ll shine a light on this cryptic menace, dissecting its anatomy and revealing its impact.

What Is a Buffer Overflow?

Imagine a bookshelf with limited space. If you try to stuff more books onto it than it can hold, chaos ensues. Similarly, in programming, a buffer overflow occurs when data spills beyond the allocated memory space. The result? Overwritten memory, crashes, and potential security breaches.

CVE-2020–19186: The Intruder

The Crime Scene

In the nc_find_entry function within tinfo/comp_hash.c, a vulnerability lies dormant. Crafty attackers can exploit this weakness by sending a carefully crafted command.

The Attack Scenario

1. Our unsuspecting victim, ncurses 6.1, processes input.
2. The attacker sends a malicious command, cunningly designed to overflow the buffer.
3. The buffer, like our overstuffed bookshelf, spills its contents into forbidden territory.
4. Chaos ensues: denial of service, crashes, and potentially worse outcomes.

The Technical Details

The Vulnerable Code

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_nc_find_entry(void *table, const char *name, int create, int *errp)
{
    // ...
    if (create) {
        // Allocate memory for the entry
        entry = malloc(sizeof(*entry));
        if (entry == 0) {
            // Handle memory allocation failure
            *errp = ENOMEM;
            return 0;
        }
        // Copy the name into the entry
        entry->name = strdup(name);
        // ...
    }
    // ...
}

The Exploit

Imagine an attacker sending a command like this:

$ ncurses_app "A" * 1000000

The nc_find_entry function dutifully allocates memory for the entry, but the name is a million characters long. The buffer overflows, chaos ensues, and our digital castle crumbles.

Mitigation Strategies

1. Patch It: Keep your software up-to-date. Developers have patched this vulnerability, so update your ncurses library.
2. Boundary Checks: Implement strict boundary checks in your code. Don’t let rogue commands breach the castle walls.
3. Security Tools: Use tools like Shodan and IoT Inspector to scan for vulnerable devices. Vigilance is key.

Remember, even in the darkest corners of code, vigilance prevails. By understanding and addressing vulnerabilities like CVE-2020–19186, we fortify our digital defenses. So, fellow cyber knights, patch, protect, and keep the shadows at bay!