CVE-2021-3671 Explained : Impact and Mitigation

A null pointer de-reference was found in the way samba kerberos server handled missing sname in TGS-REQ. An authenticated user could use this flaw to crash the samba server.

Understanding CVE-2021-3671

This CVE involves a null pointer de-reference vulnerability in Samba's Kerberos server, allowing an authenticated user to crash the server.

What is CVE-2021-3671?

CVE-2021-3671 is a security vulnerability in Samba where a null pointer de-reference issue was discovered in the way the Samba Kerberos server dealt with missing sname in TGS-REQ. This flaw enables an authenticated user to crash the Samba server.

The Impact of CVE-2021-3671

The impact of this CVE is that an attacker could potentially exploit the vulnerability to cause a denial of service (DoS) by crashing the Samba server, affecting its availability.

Technical Details of CVE-2021-3671

This section delves into the vulnerability description, affected systems, and the exploitation mechanism.

Vulnerability Description

The vulnerability involves a null pointer de-reference in Samba's Kerberos server, triggered by missing sname in TGS-REQ, which can be utilized by an authenticated user to crash the server.

Affected Systems and Versions

The affected system is Samba, with versions such as samba 4.13.12 and samba 4.14.8 being impacted. These versions have been identified as vulnerable to this security issue.

Exploitation Mechanism

An authenticated attacker can exploit the null pointer de-reference vulnerability by manipulating the sname in TGS-REQ, potentially leading to a server crash.

Mitigation and Prevention

This section covers immediate steps to take and long-term security practices to safeguard against CVE-2021-3671.

Immediate Steps to Take

Users are advised to update Samba to versions 4.13.12 or 4.14.8 to mitigate the vulnerability and prevent exploitation by malicious actors.

Long-Term Security Practices

Implementing robust authentication mechanisms, monitoring server activity, and staying updated on security advisories are essential to enhance the overall security posture.

Patching and Updates

Regularly applying patches and updates released by Samba to address known vulnerabilities ensures the system remains protected from potential threats.