CVE-2018-5737 in BIND
Summary
by MITRE
A problem with the implementation of the new serve-stale feature in BIND 9.12 can lead to an assertion failure in rbtdb.c, even when stale-answer-enable is off. Additionally, problematic interaction between the serve-stale feature and NSEC aggressive negative caching can in some cases cause undesirable behavior from named, such as a recursion loop or excessive logging. Deliberate exploitation of this condition could cause operational problems depending on the particular manifestation -- either degradation or denial of service. Affects BIND 9.12.0 and 9.12.1.
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Analysis
by VulDB Data Team • 03/14/2023
The vulnerability identified as CVE-2018-5737 represents a critical flaw in the BIND 9.12 DNS server implementation that specifically targets the serve-stale feature functionality. This issue manifests in the rbtdb.c source file where an assertion failure occurs regardless of the stale-answer-enable configuration setting, creating a fundamental instability in the DNS resolution process. The vulnerability affects versions 9.12.0 and 9.12.1 of the BIND software, which are widely deployed across enterprise and internet infrastructure, making this a significant concern for network security operations.
The technical implementation flaw stems from improper handling of the serve-stale feature when combined with NSEC aggressive negative caching mechanisms within the DNS server's recursive resolution process. When these two features interact, they create a condition where the named daemon can enter into recursive loops or generate excessive logging entries that overwhelm system resources. This interaction demonstrates a classic example of how seemingly independent features can create cascading failures when integrated into complex software systems. The vulnerability operates at the core DNS resolution layer, affecting the fundamental trust and reliability of DNS infrastructure that underpins internet connectivity.
The operational impact of this vulnerability extends beyond simple service degradation to potentially enabling full denial of service conditions that can disrupt critical network operations. The recursive loop behavior can consume excessive CPU cycles and memory resources, while the excessive logging can fill disk space and create performance bottlenecks that affect legitimate DNS queries. This vulnerability particularly impacts environments where DNS servers handle high volumes of recursive queries, as the conditions can rapidly escalate from minor performance issues to complete service outages. The potential for deliberate exploitation means that malicious actors could intentionally trigger these conditions to disrupt DNS services, making this vulnerability particularly dangerous in production environments.
Mitigation strategies for CVE-2018-5737 should focus on immediate patching of affected BIND versions to 9.12.2 or later, which contains the necessary fixes for the rbtdb.c assertion failure and the serve-stale feature interactions. Organizations should also consider temporarily disabling the serve-stale feature if immediate patching is not feasible, though this may impact the availability of stale data for certain DNS resolution scenarios. Network administrators should implement monitoring solutions to detect recursive loop conditions and excessive logging patterns that may indicate exploitation attempts. The vulnerability aligns with CWE-248, representing an unchecked runtime error that can lead to system instability and denial of service conditions. From an ATT&CK framework perspective, this vulnerability could be categorized under T1499.004 for network disruption and T1566.001 for initial access through service exploitation, making it a significant concern for both defensive and offensive security operations.