CVE-2023-35994: Critical Array Index Validation Vulnerabilities in GTKWave

Overview

This article discusses a critical vulnerability identified as CVE-2023-35994 that exists in the popular open-source waveform viewer, GTKWave. This vulnerability specifically affects the ‘fstReaderIterBlocks2 tdelta’ functionality of GTKWave version 3.3.115. Cybersecurity researchers have found that it can be exploited via a carefully crafted .fst file leading to arbitrary code execution. The severity of this vulnerability stems from the fact that it can potentially lead to system compromise or data leakage, posing a significant risk to users and organizations using the affected software version.

Vulnerability Summary

CVE ID: CVE-2023-35994
Severity: High (7.8 CVSS)
Attack Vector: Opening a malicious .fst file
Privileges Required: None
User Interaction: Required
Impact: System compromise and data leakage

Affected Products

Product | Affected Versions

GTKWave | 3.3.115

How the Exploit Works

This exploit takes advantage of improper array index validation vulnerabilities in the ‘fstReaderIterBlocks2 tdelta’ functionality of GTKWave. An attacker crafts a malicious .fst file and sends it to the victim. Once the victim opens this file using GTKWave, the software fails to properly validate the array indexes within the file. This failure allows the attacker to execute code arbitrarily on the victim’s system, potentially leading to system compromise or data leakage.

Conceptual Example Code

Although the exact nature of the exploit code will vary based on the attacker’s intent, a conceptual example might look like this:

block
{
type: tdelta
index: 99999999999
payload: {
"executable_code": "malicious code here"
}
}

In this example, the “index” value is higher than what the application can handle, and the “executable_code” contains the attacker’s malicious code to be executed on the target system.

Mitigation Guidance

To mitigate this vulnerability, users are advised to apply the vendor patch as soon as it becomes available. Until then, users can use a Web Application Firewall (WAF) or Intrusion Detection System (IDS) as a temporary mitigation measure. These systems can help detect and block attempts to exploit this vulnerability. Also, users should be cautious while opening .fst files from unknown sources.