CVE-2021-39921 Explained : Impact and Mitigation

CVE-2021-39921, assigned by GitLab, involves a NULL pointer exception in the Modbus dissector in Wireshark versions 3.4.0 to 3.4.9 and 3.2.0 to 3.2.17, which allows for denial of service via packet injection or crafted capture file.

Understanding CVE-2021-39921

This section provides insights into the nature and impact of CVE-2021-39921.

What is CVE-2021-39921?

CVE-2021-39921 is a vulnerability in Wireshark that stems from a NULL pointer exception, potentially leading to denial of service when processing certain packets or files.

The Impact of CVE-2021-39921

The vulnerability's impact is rated as HIGH with a CVSS V3.1 base score of 7.5. It can be exploited over a network without requiring privileges, impacting the availability of affected systems.

Technical Details of CVE-2021-39921

Explore the specific technical aspects of the CVE-2021-39921 vulnerability.

Vulnerability Description

The vulnerability arises from a NULL pointer dereference in Wireshark, specifically in the Modbus dissector, exposing systems to denial of service attacks.

Affected Systems and Versions

Vendor: Wireshark Foundation
Product: Wireshark
Affected Versions:
Version >=3.4.0, <3.4.10
Version >=3.2.0, <3.2.18

Exploitation Mechanism

The vulnerability can be exploited through packet injection or by using specially crafted capture files to trigger the NULL pointer exception.

Mitigation and Prevention

Learn how to address and prevent CVE-2021-39921 effectively.

Immediate Steps to Take

Apply the patches provided by Wireshark Foundation to upgrade to non-vulnerable versions.
Monitor network traffic for any suspicious activities that could indicate exploitation of the vulnerability.
Consider blocking Modbus traffic until systems are patched.

Long-Term Security Practices

Keep network monitoring tools and security software up to date to detect potential vulnerabilities promptly.
Educate network administrators and security professionals on best practices for handling and mitigating vulnerabilities.

Patching and Updates

Regularly check for security updates and patches from Wireshark Foundation to address vulnerabilities promptly.