CVE-2007-0494 in BIND
Summary
by MITRE
ISC BIND 9.0.x, 9.1.x, 9.2.0 up to 9.2.7, 9.3.0 up to 9.3.3, 9.4.0a1 up to 9.4.0a6, 9.4.0b1 up to 9.4.0b4, 9.4.0rc1, and 9.5.0a1 (Bind Forum only) allows remote attackers to cause a denial of service (exit) via a type * (ANY) DNS query response that contains multiple RRsets, which triggers an assertion error, aka the "DNSSEC Validation" vulnerability.
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Analysis
by VulDB Data Team • 07/14/2019
The CVE-2007-0494 vulnerability represents a critical denial of service flaw in ISC BIND versions ranging from 9.0.x through 9.5.0a1, specifically affecting the DNSSEC validation functionality. This vulnerability operates through a carefully crafted DNS response that contains multiple resource record sets within a single type * (ANY) query response, ultimately triggering an assertion error that causes the DNS server to exit unexpectedly. The flaw fundamentally impacts the stability and availability of DNS services, as it allows remote attackers to disrupt DNS resolution capabilities without requiring authentication or privileged access.
The technical implementation of this vulnerability stems from improper handling of DNS responses during DNSSEC validation processes. When BIND receives a type * (ANY) query response containing multiple RRsets, the validation logic fails to properly process the multiple record sets, leading to an assertion failure that terminates the server process. This behavior manifests as an assertion error within the DNSSEC validation subsystem, which is designed to validate DNS security extensions but becomes a point of failure when encountering malformed responses with multiple RRsets. The vulnerability specifically affects the validation logic that processes DNS responses during DNSSEC validation, where the software fails to handle the edge case of multiple RRsets within a single response properly.
The operational impact of this vulnerability extends beyond simple service disruption, as it can be exploited by remote attackers to systematically degrade DNS infrastructure availability. Since the flaw occurs during normal DNS query processing and requires no authentication, it represents a significant risk to organizations relying on BIND DNS servers for critical infrastructure services. The vulnerability essentially creates a condition where any attacker can cause a DNS server to crash and exit, potentially leading to cascading failures in network services that depend on DNS resolution. This makes the vulnerability particularly dangerous in environments where DNS availability is critical for business operations or where the DNS infrastructure serves as a foundation for other security services.
Organizations affected by this vulnerability should prioritize immediate patching of their BIND installations to versions that address the DNSSEC validation assertion error. The mitigation strategy involves upgrading to BIND versions that contain fixes for the specific assertion failure in the DNSSEC validation code path, typically found in BIND 9.2.8, 9.3.4, 9.4.1, and later releases. Network administrators should also consider implementing additional monitoring and alerting for DNS server processes to detect unexpected exits or restarts that may indicate exploitation attempts. From a cybersecurity perspective, this vulnerability aligns with ATT&CK technique T1499.004 for network denial of service and CWE-248 for an unspecified weakness in the assertion mechanism. The vulnerability demonstrates how complex validation logic in security-critical software can introduce unexpected failure modes that adversaries can exploit to cause system instability, emphasizing the importance of comprehensive testing and validation of security features in DNS infrastructure software.