CVE-2019-6643 in BIG-IP
Summary
by MITRE
On versions 14.1.0-14.1.0.5, 14.0.0-14.0.0.4, 13.0.0-13.1.2, 12.1.0-12.1.4.1, and 11.5.2-11.6.4, an attacker sending specifically crafted DHCPv6 requests through a BIG-IP virtual server configured with a DHCPv6 profile may be able to cause the TMM process to produce a core file.
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Analysis
by VulDB Data Team • 12/13/2023
The vulnerability identified as CVE-2019-6643 represents a critical denial of service weakness in F5 BIG-IP systems that affects multiple version ranges including 14.1.0-14.1.0.5, 14.0.0-14.0.0.4, 13.0.0-13.1.2, 12.1.0-12.1.4.1, and 11.5.2-11.6.4. This flaw specifically targets the DHCPv6 profile functionality within the Traffic Management Microkernel (TMM) process, which is responsible for handling network traffic management operations. The vulnerability stems from insufficient input validation and error handling mechanisms when processing specially crafted DHCPv6 packets, creating an exploitable condition that can be leveraged by remote attackers to disrupt services.
The technical implementation of this vulnerability occurs when a malicious actor sends carefully constructed DHCPv6 requests to a BIG-IP virtual server that has a DHCPv6 profile configured. The TMM process fails to properly validate or sanitize the incoming DHCPv6 packets, leading to a condition where the process becomes unstable and generates a core dump file. This core file generation represents a complete system crash and service disruption, effectively rendering the affected virtual server unavailable to legitimate users. The flaw operates at the protocol parsing layer, where the system does not adequately handle malformed or unexpected DHCPv6 packet structures, causing memory corruption or stack overflow conditions that terminate the TMM process.
From an operational impact perspective, this vulnerability poses significant risk to enterprise networks that rely on F5 BIG-IP appliances for load balancing and traffic management services. The disruption caused by the TMM process crash can lead to complete service outages for applications and services that depend on these appliances, potentially affecting thousands of users and generating substantial business impact. The vulnerability is particularly dangerous because it requires minimal privileges to exploit, as attackers only need to send specific network packets to the configured virtual server, making it an attractive target for both opportunistic and targeted attacks. Network administrators may experience service degradation or complete loss of availability for critical infrastructure components, especially in environments where BIG-IP appliances serve as primary traffic managers.
The exploitation of CVE-2019-6643 aligns with attack patterns documented in the MITRE ATT&CK framework under the T1499 category for network denial of service, where adversaries target network infrastructure to disrupt services. This vulnerability is classified as a CWE-121 stack-based buffer overflow or CWE-129 improper input validation, both of which represent fundamental security weaknesses in software design and implementation. Organizations should implement immediate mitigation strategies including applying the latest F5 security patches, configuring network access controls to restrict DHCPv6 traffic to trusted sources, and implementing monitoring solutions to detect abnormal core file generation patterns. Additionally, network segmentation and firewall rules can help limit the attack surface by preventing unauthorized access to virtual servers configured with DHCPv6 profiles. Regular security assessments and vulnerability scanning should be conducted to identify systems running affected versions and ensure proper patch management protocols are in place to prevent exploitation attempts.