CVE-2019-6612 in BIG-IP
Summary
by MITRE
On BIG-IP 14.0.0-14.1.0.1, 13.0.0-13.1.1.4, 12.1.0-12.1.4, 11.6.1-11.6.3.4, and 11.5.2-11.5.8, DNS query TCP connections that are aborted before receiving a response from a DNS cache may cause TMM to restart.
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Analysis
by VulDB Data Team • 09/12/2023
The vulnerability identified as CVE-2019-6612 affects F5 BIG-IP appliances across multiple version ranges including 14.0.0 through 14.1.0.1, 13.0.0 through 13.1.1.4, 12.1.0 through 12.1.4, 11.6.1 through 11.6.3.4, and 11.5.2 through 11.5.8. This issue specifically targets the Traffic Management Microkernel (TMM) component responsible for handling network traffic processing. The flaw manifests when TCP connections initiated for DNS queries are abruptly terminated before receiving responses from DNS cache servers, resulting in unexpected system restarts that can disrupt network services and compromise availability.
The technical root cause of this vulnerability lies in improper error handling within the TMM's DNS query processing mechanism. When a client initiates a TCP DNS query and subsequently aborts the connection before the DNS server responds, the TMM fails to properly manage this exceptional condition. This inadequate state management leads to memory corruption or resource handling failures that ultimately trigger a complete system restart. The vulnerability represents a classic example of improper exception handling and resource cleanup, which aligns with CWE-404, which describes improper resource cleanup or release, and CWE-704, which covers incorrect behavior ordering or incorrect control flow.
The operational impact of CVE-2019-6612 extends beyond simple service disruption to encompass potential denial of service scenarios that can severely impact business operations. Network administrators face the challenge of unpredictable system restarts that can occur during normal DNS query processing, particularly when dealing with malicious actors who might exploit this vulnerability to repeatedly initiate and abort DNS connections. The restart behavior creates a cascading effect where legitimate DNS services are interrupted, potentially affecting downstream applications and services that depend on name resolution. This vulnerability directly maps to attack techniques described in the MITRE ATT&CK framework under T1499, which covers network denial of service attacks, and T1566, which addresses credential harvesting through network attacks.
Mitigation strategies for this vulnerability require immediate implementation of F5's official security patches and updates. Organizations should prioritize applying the vendor-provided fixes as soon as possible since the vulnerability can be exploited to cause system restarts without requiring authentication or specialized tools. Network administrators should also implement monitoring solutions to detect abnormal connection patterns and sudden system restarts that might indicate exploitation attempts. Additional protective measures include implementing rate limiting on DNS query connections, configuring firewalls to restrict unnecessary DNS traffic, and maintaining robust backup and recovery procedures to minimize downtime during potential exploitation events. The vulnerability demonstrates the critical importance of proper error handling in network infrastructure components and highlights the need for comprehensive security testing of edge services that handle external network communications.