CVE-2023-37573: Multiple use-after-free vulnerabilities in GTKWave 3.3.115

Overview

In this blog post, we will examine the CVE-2023-37573 vulnerability, a serious security flaw that affects GTKWave 3.3.115. This vulnerability is significant due to its potential to lead to arbitrary code execution when a specially crafted .vcd file is opened. The vulnerability is triggered by the GUI’s recoder VCD parsing code, and it’s particularly concerning for users of this version of GTKWave as it could potentially lead to system compromise or data leakage.

Vulnerability Summary

CVE ID: CVE-2023-37573
Severity: High (7.8)
Attack Vector: Local
Privileges Required: None
User Interaction: Required
Impact: System compromise, data leakage

Affected Products

Product | Affected Versions

GTKWave | 3.3.115

How the Exploit Works

The vulnerability lies in the get_vartoken realloc function of GTKWave 3.3.115. The function is responsible for reallocating memory resources during the parsing of .vcd files. However, the function maintains a reference to a memory location even after it has been freed, leading to a use-after-free vulnerability.
When a specially crafted .vcd file is opened, the function can be manipulated to reference this deallocated memory space. This manipulation can lead to arbitrary code execution as the malicious code inserted in this space gets executed.

Conceptual Example Code

While we don’t encourage or condone malicious activities, a conceptual example of this vulnerability might look something like this:

#include<stdio.h>
#include<stdlib.h>
int main() {
// Allocate memory
char *ptr = malloc(8);
// Use memory
strcpy(ptr, "GTKWave");
// Free memory
free(ptr);
// Here's where the use-after-free vulnerability is created.
// We're using 'ptr' after it has been freed.
strcpy(ptr, "Malicious code");
return 0;
}

In this conceptual example, the malicious code could be anything, from a payload that creates a backdoor to one that leaks sensitive data.

Mitigation

The most effective way to rectify this vulnerability is to apply the vendor patch once it becomes available. Until then, using a Web Application Firewall (WAF) or Intrusion Detection System (IDS) can offer temporary mitigation. Users are also advised to avoid opening .vcd files from untrusted sources.