CVE-2017-15908 : Security Advisory and Response

CVE-2017-15908 was published on October 26, 2017, by MITRE. It involves a vulnerability in systemd versions 223 to 235 that allows a remote DNS server to trigger a denial of service (DoS) attack by exploiting the 'systemd-resolved' service.

Understanding CVE-2017-15908

This CVE entry highlights a specific vulnerability in systemd that can be exploited remotely, potentially leading to a DoS attack.

What is CVE-2017-15908?

In systemd versions 223 to 235, a flaw exists where a specially crafted DNS NSEC resource record can cause the 'systemd-resolved' service's dns_packet_read_type_window() function to enter an endless loop, resulting in a DoS attack.

The Impact of CVE-2017-15908

The vulnerability allows a remote attacker to exploit the systemd service, leading to a denial of service condition for the affected service.

Technical Details of CVE-2017-15908

This section delves into the technical aspects of the vulnerability.

Vulnerability Description

The flaw in systemd versions 223 to 235 allows a remote DNS server to send a malicious DNS NSEC resource record, triggering an infinite loop in the 'systemd-resolved' service and causing a DoS.

Affected Systems and Versions

Affected versions: 223 to 235 of systemd
Systems running systemd within this version range are vulnerable to exploitation.

Exploitation Mechanism

By sending a specially designed DNS NSEC resource record, an attacker can exploit the 'systemd-resolved' service, causing it to enter an endless loop and resulting in a DoS attack.

Mitigation and Prevention

To address CVE-2017-15908, consider the following mitigation strategies:

Immediate Steps to Take

Update systemd to a non-vulnerable version.
Implement network security measures to prevent unauthorized access.

Long-Term Security Practices

Regularly update and patch software to mitigate known vulnerabilities.
Monitor network traffic for suspicious activities that may indicate an ongoing attack.

Patching and Updates

Apply patches provided by the vendor to fix the vulnerability.
Stay informed about security advisories and updates related to systemd.