CVE-2018-21029 : Exploit Details and Defense Strategies

Certificates issued by trusted certificate authorities are accepted by systemd versions 239 to 245 for DNS Over TLS. The absence of hostname validation in the GnuTLS backend has been disputed as a vulnerability.

Understanding CVE-2018-21029

This CVE involves the acceptance of certificates by systemd versions 239 to 245 without hostname validation.

What is CVE-2018-21029?

systemd versions 239 to 245 accept certificates from trusted CAs for DNS Over TLS without hostname validation.
The absence of Server Name Indication (SNI) transmission is a key aspect of this vulnerability.

The Impact of CVE-2018-21029

The vulnerability allows the acceptance of any certificate signed by a trusted CA without hostname verification.
The developer has contested this as not being a vulnerability due to the specific context where no hostname needs to be transmitted.

Technical Details of CVE-2018-21029

This section provides detailed technical information about the vulnerability.

Vulnerability Description

systemd versions 239 to 245 accept certificates from trusted CAs for DNS Over TLS without verifying the hostname.

Affected Systems and Versions

Affected versions: systemd 239 to 245

Exploitation Mechanism

Attackers can exploit this vulnerability by using certificates signed by trusted CAs without proper hostname validation.

Mitigation and Prevention

Steps to address and prevent the CVE-2018-21029 vulnerability.

Immediate Steps to Take

Update systemd to a non-vulnerable version.
Implement additional security measures for DNS Over TLS.

Long-Term Security Practices

Regularly update and patch systemd to the latest version.
Implement secure configurations for DNS encryption.

Patching and Updates

Apply patches provided by systemd to address the vulnerability.