CVE-2022-33992 in Domain Name Relay Daemon
Summary
by MITRE • 08/15/2022
DNRD (aka Domain Name Relay Daemon) 2.20.3 forwards and caches DNS queries with the CD (aka checking disabled) bit set to 1. This leads to disabling of DNSSEC protection provided by upstream resolvers.
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Analysis
by VulDB Data Team • 08/15/2022
The DNRD vulnerability CVE-2022-33992 represents a critical security flaw in the Domain Name Relay Daemon version 2.20.3 that fundamentally undermines DNS security mechanisms. This vulnerability specifically targets the handling of DNS queries where the Checking Disabled (CD) bit is set to 1, which is a crucial indicator that the client has intentionally disabled DNSSEC validation. The daemon's improper handling of this bit results in the forwarding and caching of DNS responses without maintaining the original security context, effectively bypassing the DNSSEC protections that upstream resolvers are designed to provide.
The technical implementation of this vulnerability stems from DNRD's failure to properly preserve the CD bit during DNS query forwarding operations. When a DNS client sets the CD bit, it explicitly communicates to recursive resolvers that it does not want DNSSEC validation to be performed, typically for performance reasons or when operating in environments where DNSSEC validation might cause issues. However, DNRD 2.20.3 fails to maintain this security context when forwarding queries to upstream servers, leading to a scenario where the CD bit is set to 1 in the forwarded query regardless of the original intent. This behavior creates a security degradation where DNSSEC validation is disabled even when upstream resolvers would have otherwise performed this crucial security function.
The operational impact of this vulnerability extends beyond simple query forwarding, as it fundamentally compromises the integrity of DNS resolution within networks that rely on DNRD for DNS services. Attackers can exploit this weakness to perform cache poisoning attacks more effectively by leveraging the disabled DNSSEC protections, potentially leading to man-in-the-middle attacks or redirection of traffic to malicious endpoints. The vulnerability affects any network infrastructure using DNRD 2.20.3 as a DNS relay or caching server, making it particularly concerning for enterprise environments where DNS security is paramount. This flaw directly violates the principle of least privilege and proper security context preservation that should be maintained throughout DNS resolution processes.
Organizations affected by this vulnerability should immediately implement mitigations including updating to DNRD versions that properly handle the CD bit, configuring the daemon to preserve DNSSEC validation settings during forwarding operations, and implementing additional network monitoring to detect anomalous DNS traffic patterns. The vulnerability aligns with CWE-200, which addresses information exposure, and represents a significant deviation from established DNS security practices. From an ATT&CK perspective, this vulnerability could be leveraged during the initial access and persistence phases of an attack, allowing adversaries to undermine DNS security controls that would normally prevent malicious domain resolution. The recommended remediation involves not only patching the software but also implementing proper DNS security monitoring and ensuring that all DNS infrastructure components maintain consistent security contexts throughout the resolution process, thereby preventing the accidental disabling of critical DNSSEC protections that are essential for maintaining network integrity and security.