CZ.NIC Knot Resolver CVE-2019-19331 Denial of Service Vulnerability

Description

CZ.NIC Knot Resolver is prone to a denial-of-service vulnerability. Remote attackers can exploit this issue to cause denial-of-service condition. Knot Resolver versions prior to 4.3.0 are vulnerable.

Technologies Affected

• CZ.NIC labs Knot Resolver 2.0.0
• CZ.NIC labs Knot Resolver 2.1.0
• CZ.NIC labs Knot Resolver 2.2.0
• CZ.NIC labs Knot Resolver 2.3.0
• CZ.NIC labs Knot Resolver 2.4.0
• CZ.NIC labs Knot Resolver 3.0.0
• CZ.NIC labs Knot Resolver 3.1.0
• CZ.NIC labs Knot Resolver 3.2.0
• CZ.NIC labs Knot Resolver 4.0.0
• CZ.NIC labs Knot Resolver 4.1.0
• CZ.NIC labs Knot Resolver 4.2.0
• CZ.NIC labs Knot Resolver 4.2.1
• CZ.NIC labs Knot Resolver 4.2.2

Recommendations

Block external access at the network boundary, unless external parties require service.
If global access isn’t needed, filter access to the affected computer at the network boundary. Restricting access to only trusted computers and networks might greatly reduce the likelihood of successful exploits.

Deploy network intrusion detection systems to monitor network traffic for malicious activity.
Deploy NIDS to detect and block attacks and anomalous activity such as requests containing suspicious URI sequences. Since the webserver may log such requests, review logs regularly.

Updates are available. Please see the references or vendor advisory for more information.