CVE-2021-28543 : Security Advisory and Response

Varnish varnish-modules before 0.17.1 is vulnerable to a denial of service attack, allowing remote attackers to trigger a daemon restart under certain configurations. This can impact the overall availability and performance of systems running Varnish Cache and varnish-modules.

Understanding CVE-2021-28543

This CVE highlights a vulnerability in Varnish varnish-modules that can be exploited by remote attackers to cause a denial of service attack by triggering a daemon restart.

What is CVE-2021-28543?

CVE-2021-28543 relates to a vulnerability in Varnish varnish-modules before version 0.17.1 that enables remote attackers to restart the Varnish Cache daemon, impacting system availability and performance.

The Impact of CVE-2021-28543

The vulnerability allows attackers to cause a Varnish Cache restart, leading to increased cache misses, reduced availability, and potential strain on backend servers.

Technical Details of CVE-2021-28543

This section provides more in-depth technical insights into the vulnerability.

Vulnerability Description

The issue arises from assertion failures or NULL pointer dereferences triggered in Varnish Cache through specific functions in varnish-modules, providing the opportunity for a remote restart.

Affected Systems and Versions

Varnish varnish-modules versions before 0.17.1 are affected by this vulnerability, impacting systems that install both Varnish Cache and varnish-modules.

Exploitation Mechanism

Remote clients can exploit the vulnerability through certain Varnish Configuration Language (VCL) files to initiate a Varnish Cache restart.

Mitigation and Prevention

To mitigate the risks associated with CVE-2021-28543, immediate action and long-term security practices are essential.

Immediate Steps to Take

Organizations should update Varnish varnish-modules to version 0.17.1 or apply patches provided by the vendor. Monitoring system logs for potential restart events is also recommended.

Long-Term Security Practices

Regularly update and patch Varnish-related software to address known vulnerabilities and maintain system security. Additionally, implement network security measures to prevent unauthorized access.

Patching and Updates

Stay informed about security advisories and updates from Varnish Cache and varnish-modules to address vulnerabilities promptly.