PowerDNS Security Advisory 2022-02: incomplete exception handling related to protobuf message generation

• CVE: CVE-2022-37428
• Date: 23th of August 2022.
• Affects: PowerDNS Recursor up to and including 4.5.9, 4.6.2 and 4.7.1
• Not affected: PowerDNS Recursor 4.5.10, 4.6.3 and 4.7.2
• Severity: Medium
• Impact: Denial of service
• Exploit: This problem can be triggered by a remote attacker with access to the recursor if protobuf logging is enabled
• Risk of system compromise: None
• Solution: Upgrade to patched version, disable protobuf logging of responses

This issue only affects recursors which have protobuf logging enabled using the

• protobufServer function with logResponses=true or
• outgoingProtobufServer function with logResponses=true

If either of these functions is used without specifying logResponses, its value is true. An attacker needs to have access to the recursor, i.e. the remote IP must be in the access control list. If an attacker queries a name that leads to an answer with specific properties, a protobuf message might be generated that causes an exception. The code does not handle this exception correctly, causing a denial of service.