CVE-2018-14644 in Recursor
Summary
by MITRE
An issue has been found in PowerDNS Recursor from 4.0.0 up to and including 4.1.4. A remote attacker sending a DNS query for a meta-type like OPT can lead to a zone being wrongly cached as failing DNSSEC validation. It only arises if the parent zone is signed, and all the authoritative servers for that parent zone answer with FORMERR to a query for at least one of the meta-types. As a result, subsequent queries from clients requesting DNSSEC validation will be answered with a ServFail.
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Analysis
by VulDB Data Team • 06/05/2023
The vulnerability identified as CVE-2018-14644 represents a significant DNS security flaw affecting PowerDNS Recursor versions 4.0.0 through 4.1.4. This issue stems from improper handling of DNS meta-types such as OPT (Option) during recursive resolution processes. The vulnerability operates through a specific chain of conditions that can lead to incorrect DNSSEC validation caching, ultimately resulting in service degradation and potential denial of service. The flaw demonstrates a critical weakness in how the recursor processes DNS queries involving meta-types and their interaction with DNSSEC validation mechanisms.
The technical implementation of this vulnerability exploits the interaction between DNS meta-types and DNSSEC validation caching within the PowerDNS Recursor. When a remote attacker crafts DNS queries containing meta-types like OPT and directs them to a vulnerable recursor, the system can incorrectly cache zone data as failing DNSSEC validation. This misconfiguration occurs specifically when the parent zone is signed and the authoritative servers for that parent zone respond with FORMERR (Format Error) to queries for at least one meta-type. The recursor's caching mechanism fails to properly distinguish between legitimate DNS errors and actual DNSSEC validation failures, leading to erroneous cache entries that persist and affect subsequent client queries.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise the integrity of DNS resolution across affected networks. When the vulnerable recursor incorrectly caches DNSSEC validation failures, subsequent client requests that require DNSSEC validation will receive SERVFAIL responses instead of proper resolution. This creates a cascading effect where legitimate DNS queries fail, potentially affecting numerous applications and services that depend on DNS resolution. The vulnerability affects DNSSEC validation specifically, which means that networks relying on DNSSEC for security assurance may experience complete breakdowns in DNS resolution for validated zones. The issue affects the fundamental trust model of DNS resolution, as clients receive incorrect validation signals that can lead to security policy violations and service unavailability.
Mitigation strategies for CVE-2018-14644 focus primarily on upgrading to patched versions of PowerDNS Recursor, specifically versions beyond 4.1.4. Organizations should also implement network-level monitoring to detect anomalous DNS query patterns that might indicate exploitation attempts. The vulnerability aligns with CWE-20 Improper Input Validation and CWE-311 Missing Encryption of Sensitive Data, as it involves improper handling of DNS query data and affects the secure transmission of DNS validation information. From an ATT&CK perspective, this vulnerability maps to T1071.004 Application Layer Protocol DNS and T1499.004 Endpoint Denial of Service, as it enables both DNS protocol manipulation and service disruption. Network administrators should also consider implementing DNS query filtering rules that can identify and block suspicious meta-type queries, while maintaining detailed logging of DNS resolution activities to detect potential exploitation attempts. The vulnerability underscores the importance of proper DNSSEC validation handling and cache management in recursive DNS servers, emphasizing that DNS infrastructure security requires careful attention to edge cases in protocol implementation.