CVE-2023-39235: Critical Out-of-Bounds Write Vulnerability in GTKWave 3.3.115

Overview

In this article, we delve deep into the CVE-2023-39235 vulnerability, a critical flaw in the GTKWave 3.3.115 software. This vulnerability exists within the autosort functionality of the VZT vzt_rd_process_block, presenting multiple out-of-bounds write opportunities. Affected systems are susceptible to arbitrary code execution, which could lead to a complete system compromise or data leakage. This vulnerability is a significant concern for anyone using the affected versions of GTKWave, as a successful exploit could have severe implications.

Vulnerability Summary

CVE ID: CVE-2023-39235
Severity: High (CVSS 7.8)
Attack Vector: File-based
Privileges Required: None
User Interaction: Required
Impact: Arbitrary code execution, potential system compromise or data leakage

Affected Products

Product | Affected Versions

GTKWave | 3.3.115

How the Exploit Works

The CVE-2023-39235 vulnerability originates from an out-of-bounds write within the autosort functionality of VZT’s vzt_rd_process_block. An attacker could craft a malicious .vzt file that, when opened by a victim, takes advantage of the software’s handling of ‘lt->num_time_ticks’. The software fails to properly validate and constrain this input, leading to an out-of-bounds write. This vulnerability permits an attacker to execute arbitrary code on the victim’s system.

Conceptual Example Code

In this conceptual example, the vulnerability might be exploited through a malicious .vzt file containing crafted data. This pseudocode illustrates how this might be achieved:

# Pseudocode
class MaliciousVztFile:
def __init__(self):
self.num_time_ticks = self.calculate_overflow_value()
def calculate_overflow_value(self):
# Calculation here depends on the specific memory layout and architecture
# of the target system. The value should be large enough to cause
# an out-of-bounds write.
return overflow_value
malicious_file = MaliciousVztFile()
malicious_file.save_as(".vzt")

This pseudocode creates a malicious .vzt file that contains an exceedingly large ‘num_time_ticks’ value, which would lead to an out-of-bounds write and potentially arbitrary code execution when the file is opened in GTKWave.

Fix and Mitigation

To mitigate the risk of the CVE-2023-39235 vulnerability, it is recommended to apply any vendor-supplied patch as soon as possible. If a patch is not immediately available, using a Web Application Firewall (WAF) or an Intrusion Detection System (IDS) could serve as temporary mitigation. However, these measures would not fully remediate the vulnerability and should be used in conjunction with a patch when it becomes available.