CVE-2023-35955: Heap-Based Buffer Overflow Vulnerabilities in GTKWave

Overview

In this blog post, we will delve into the details of a serious cybersecurity vulnerability, CVE-2023-35955, that affects the GTKWave 3.3.115. This vulnerability is particularly significant due to its potential to lead to arbitrary code execution, resulting in potential system compromise or data leakage. The severity of the issue is further underscored by its CVSS Severity Score of 7.8. The vulnerability specifically originates from multiple heap-based buffer overflow vulnerabilities in the fstReaderIterBlocks2 VCDATA parsing functionality of the software.

Vulnerability Summary

CVE ID: CVE-2023-35955
Severity: High (7.8/10)
Attack Vector: File-based (via a specially-crafted .fst file)
Privileges Required: None
User Interaction: Required (victim needs to open a malicious file)
Impact: Potential system compromise or data leakage

Affected Products

Product | Affected Versions

GTKWave | 3.3.115

How the Exploit Works

The exploit takes advantage of multiple heap-based buffer overflow vulnerabilities in the fstReaderIterBlocks2 VCDATA parsing functionality of GTKWave. Specifically, the decompression function `LZ4_decompress_safe_partial` is implicated in this vulnerability.
An attacker prepares a specially-crafted .fst file that is designed to trigger these vulnerabilities when opened. The file can be disseminated to victims through various methods, such as phishing emails or malicious downloads. Once the victim opens the malicious file, the attacker can achieve arbitrary code execution, potentially leading to system compromise or data leakage.

Conceptual Example Code

While we won’t provide an actual exploit code for ethical reasons, we can conceptualize the exploitation process.
First, an attacker would need to craft a malicious .fst file that could exploit the buffer overflow vulnerabilities. The payload of this file might look something like this:

$ echo -e "VCD2\n\$end\n\$timescale 1 ns\n\$end\n\$scope module top\n\$end\n\$var wire 1 ! clk\n\$end\n#0\n1!\n#1\n0!\n#2\n1!\n#2.5\n\$dumpvars\n0!\n\$end\n#3\n1!\n#4\n" > malicious.fst

The attacker then disseminates this file to the victim, who, upon opening it with GTKWave, triggers the buffer overflow and subsequent arbitrary code execution.

Mitigation

As a mitigation measure, users can apply the vendor-provided patch to fix this vulnerability. Alternatively, users can deploy Web Application Firewalls (WAF) or Intrusion Detection Systems (IDS) as a temporary mitigation method until the patch can be applied. Regularly updating software and keeping abreast of newly discovered vulnerabilities can help prevent such attacks.