CVE-2016-2775 in BIND
Summary
by MITRE
ISC BIND 9.x before 9.9.9-P2, 9.10.x before 9.10.4-P2, and 9.11.x before 9.11.0b2, when lwresd or the named lwres option is enabled, allows remote attackers to cause a denial of service (daemon crash) via a long request that uses the lightweight resolver protocol.
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Analysis
by VulDB Data Team • 09/06/2022
The vulnerability identified as CVE-2016-2775 affects ISC BIND versions prior to specific patch releases, creating a critical denial of service condition through the lightweight resolver protocol implementation. This flaw specifically impacts systems where the lwresd daemon or named lwres option is enabled, representing a significant risk to network infrastructure services that rely on DNS resolution capabilities. The vulnerability stems from inadequate input validation within the lightweight resolver functionality, which processes external DNS requests through a simplified protocol designed to reduce resource consumption compared to traditional DNS operations.
The technical exploitation of this vulnerability occurs when remote attackers craft specially formatted DNS requests that exceed predetermined buffer limits within the lwres implementation. These malformed requests trigger memory corruption conditions that cause the affected BIND daemon to crash and restart automatically, effectively disrupting DNS services for legitimate users. The flaw operates at the protocol level where the lightweight resolver processes incoming requests without proper bounds checking on request parameters, particularly focusing on request length validation. This type of vulnerability maps directly to CWE-121, which describes heap-based buffer overflow conditions, and CWE-122, addressing buffer overflow vulnerabilities that occur when insufficient space is allocated for data.
From an operational perspective, this vulnerability presents a substantial risk to organizations that depend on DNS infrastructure, as it allows attackers to perform simple denial of service attacks requiring minimal resources and technical expertise. The impact extends beyond individual service disruption to potentially affecting entire network domains that rely on the compromised DNS servers for name resolution. Attackers can leverage this vulnerability to repeatedly crash DNS services, creating persistent availability issues that may require manual intervention to restore normal operations. The lightweight resolver functionality, designed to provide efficient DNS resolution for applications, becomes a liability when improperly secured, demonstrating how optimization features can introduce security weaknesses.
Organizations should implement immediate mitigations including updating to patched versions of ISC BIND where available, disabling the lwresd functionality when not required, or applying network-level firewalls to restrict access to affected services. The ATT&CK framework categorizes this vulnerability under T1499.004, which describes network denial of service attacks, and T1595.001 for reconnaissance activities that identify target vulnerabilities. System administrators should also consider implementing monitoring solutions to detect unusual daemon restart patterns and establish automated alerting for service disruptions that may indicate exploitation attempts. The vulnerability highlights the importance of input validation in network services and the need for comprehensive security testing of protocol implementations that handle external data processing.