CVE-2018-5501 in BIG-IP
Summary
by MITRE
In some circumstances, on F5 BIG-IP systems running 13.0.0, 12.1.0 - 12.1.3.1, any 11.6.x or 11.5.x release, or 11.2.1, TCP DNS profile allows excessive buffering due to lack of flow control.
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Analysis
by VulDB Data Team • 02/16/2023
The vulnerability identified as CVE-2018-5501 affects F5 BIG-IP systems across multiple software versions including 13.0.0, 12.1.0 through 12.1.3.1, various 11.6.x and 11.5.x releases, and 11.2.1. This issue resides within the TCP DNS profile functionality of the BIG-IP platform, which is designed to handle domain name system queries and responses. The flaw represents a significant security concern as it enables malicious actors to exploit the system's buffering mechanisms without proper flow control measures. The vulnerability falls under the category of resource exhaustion and can lead to service disruption or system instability.
The technical flaw manifests in the absence of adequate flow control within the TCP DNS profile implementation. When the system processes DNS requests, it maintains buffers to handle incoming data streams. However, due to the lack of proper flow control mechanisms, an attacker can send malformed or excessive DNS queries that cause the system to allocate and maintain buffers indefinitely. This behavior results in memory exhaustion and can lead to denial of service conditions where legitimate users cannot access services through the affected BIG-IP system. The vulnerability is particularly dangerous because it operates at the network protocol level and can be exploited through standard DNS traffic without requiring authentication or specialized privileges.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise the availability of critical network services. Organizations relying on F5 BIG-IP systems for load balancing, application delivery, and security services face significant risks when this vulnerability exists in their infrastructure. The attack can be executed with minimal resources and can cause cascading failures throughout the network, especially when the affected systems are part of critical service chains. Network administrators may observe gradual performance degradation followed by complete service outages, making detection and mitigation challenging. The vulnerability affects both IPv4 and IPv6 DNS traffic processing and can be amplified through DNS amplification attacks, where small requests generate large responses that consume system resources.
Mitigation strategies for CVE-2018-5501 should include immediate implementation of firmware updates from F5 to address the flow control deficiencies in the TCP DNS profile. Organizations should also implement network-level mitigations such as rate limiting for DNS traffic, connection tracking restrictions, and monitoring for unusual buffering patterns. The implementation of proper flow control mechanisms at the application layer can help detect and prevent excessive buffer allocation. Security teams should also consider implementing intrusion detection systems that can identify abnormal DNS traffic patterns indicative of exploitation attempts. Additionally, the use of DNS security extensions and proper access controls can help reduce the attack surface. Organizations should follow the principle of least privilege and ensure that DNS services are not exposed to untrusted networks. This vulnerability aligns with CWE-400 which addresses uncontrolled resource consumption and relates to ATT&CK technique T1499.004 for network denial of service attacks, emphasizing the importance of proper resource management and flow control in network infrastructure components.