CVE-2007-0493 in BIND
Summary
by MITRE
Use-after-free vulnerability in ISC BIND 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 (named daemon crash) via unspecified vectors that cause named to "dereference a freed fetch context."
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Analysis
by VulDB Data Team • 03/15/2021
The vulnerability described in CVE-2007-0493 represents a critical use-after-free condition affecting ISC BIND versions within specific release ranges including 9.3.0 through 9.3.3, 9.4.0a1 through 9.4.0a6, 9.4.0b1 through 9.4.0b4, 9.4.0rc1, and 9.5.0a1. This flaw resides in the named daemon process that serves as the primary DNS server implementation for many internet infrastructure components. The vulnerability specifically manifests when the named daemon encounters certain network requests that trigger the dereferencing of a freed fetch context, creating a scenario where memory that has been deallocated is still being accessed by the application.
The technical nature of this vulnerability places it squarely within the CWE-416 category of use-after-free conditions, which occurs when a program continues to reference memory after it has been freed by the system. In the context of DNS server operations, this flaw can be exploited by remote attackers who craft malicious DNS queries designed to trigger the specific code path leading to the freed memory dereference. The exploitation mechanism involves sending carefully constructed DNS packets that cause the named daemon to process a fetch context that has already been freed from memory, leading to unpredictable behavior and ultimately system instability.
The operational impact of this vulnerability extends beyond simple denial of service as it can potentially be leveraged for more sophisticated attacks. When the named daemon crashes due to this use-after-free condition, it creates a service disruption that affects DNS resolution for all clients relying on that server. This represents a significant threat to network infrastructure since DNS servers are fundamental components of internet connectivity, and their failure can cascade across multiple services and applications. The vulnerability's remote exploitability means that attackers do not need physical access to the target system, making it particularly dangerous in internet-facing environments.
The exploitation of this vulnerability aligns with techniques described in the MITRE ATT&CK framework under the T1499 category of Network Denial of Service, where adversaries target network infrastructure to disrupt services. The attack surface is particularly broad since DNS servers are commonly exposed to untrusted networks and are often targets for reconnaissance and exploitation. Organizations running affected ISC BIND versions face significant risk as the vulnerability can be triggered through normal DNS query processing without requiring authentication or special privileges from the attacker. The impact is compounded by the fact that DNS infrastructure is critical for internet operations, making service disruption particularly damaging.
Mitigation strategies for this vulnerability should focus on immediate patching of affected ISC BIND versions, with administrators prioritizing updates to versions that contain the fix for the use-after-free condition. Network segmentation and access controls should be implemented to limit exposure of DNS servers to untrusted networks, while monitoring systems should be configured to detect unusual DNS query patterns that might indicate exploitation attempts. Additionally, implementing rate limiting and query validation mechanisms can help reduce the effectiveness of exploitation attempts while maintaining legitimate service availability. The vulnerability serves as a reminder of the importance of regular security updates and proper memory management practices in critical infrastructure software, particularly for components that handle network traffic and serve as foundational internet services.