CVE-2019-16866 Explained : Impact and Mitigation

Unbound before version 1.9.4 has a vulnerability that allows remote attackers to trigger a crash via a crafted NOTIFY query. The flaw stems from accessing uninitialized memory.

Understanding CVE-2019-16866

Versions of Unbound prior to 1.9.4 have a security issue that can be exploited by remote attackers.

What is CVE-2019-16866?

Unbound versions before 1.9.4 can access uninitialized memory, enabling remote attackers to cause a crash by sending a specially crafted NOTIFY query.

The Impact of CVE-2019-16866

Remote attackers can exploit this vulnerability to crash the system by sending a specific type of query.
The source IP address of the query must align with an access-control rule for successful exploitation.

Technical Details of CVE-2019-16866

Unbound vulnerability details and affected systems.

Vulnerability Description

Unbound versions prior to 1.9.4 have a flaw that allows unauthorized access to uninitialized memory, leading to a crash when triggered by a crafted NOTIFY query.

Affected Systems and Versions

Product: Unbound
Vendor: NLnet Labs
Versions: All versions before 1.9.4

Exploitation Mechanism

Remote attackers can exploit this vulnerability by sending a specially crafted NOTIFY query that triggers the uninitialized memory access, causing a crash.

Mitigation and Prevention

Steps to mitigate and prevent the CVE-2019-16866 vulnerability.

Immediate Steps to Take

Update Unbound to version 1.9.4 or later to mitigate the vulnerability.
Implement network-level controls to restrict access to the affected service.

Long-Term Security Practices

Regularly update software and apply security patches promptly.
Monitor security mailing lists and advisories for any new vulnerabilities related to Unbound.

Patching and Updates

Apply the security updates provided by the vendor promptly to address the vulnerability.