CVE-2019-6592 in BIG-IP
Summary
by MITRE
On BIG-IP 14.1.0-14.1.0.1, TMM may restart and produce a core file when validating SSL certificates in client SSL or server SSL profiles.
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Analysis
by VulDB Data Team • 07/19/2023
The vulnerability identified as CVE-2019-6592 affects F5 BIG-IP systems running versions 14.1.0 through 14.1.0.1, specifically targeting the Traffic Management Microkernel (TMM) component responsible for SSL certificate validation. This issue represents a denial of service condition that can be triggered during normal SSL traffic processing, potentially disrupting critical network services. The vulnerability manifests when the TMM process encounters specific SSL certificate validation scenarios, leading to unexpected restarts and core file generation. This behavior creates an opportunity for adversaries to perform service disruption attacks against F5 BIG-IP appliances, particularly those handling SSL termination or SSL offloading functions.
The technical flaw resides in the certificate validation logic within the TMM module where malformed or specially crafted SSL certificates can cause the kernel to crash and restart automatically. This occurs during the processing of client SSL or server SSL profiles, indicating that the vulnerability affects both incoming and outgoing SSL connections. The core file generation suggests that the TMM process terminates abnormally, which could expose system internals and potentially provide attackers with information about the system configuration. The vulnerability is classified under CWE-119 as a weakness involving memory access issues during SSL certificate handling, and it aligns with ATT&CK technique T1499.004 for network denial of service attacks. The restart behavior creates a cascading effect that can impact multiple services dependent on the BIG-IP appliance's SSL capabilities.
The operational impact of this vulnerability extends beyond simple service disruption to include potential business continuity issues for organizations relying on F5 BIG-IP appliances for SSL termination. Network administrators may experience unexpected downtime during critical business hours, particularly when SSL certificates are renewed or when the system encounters certificates with specific malformed attributes. The automatic restart mechanism can lead to session drops for active SSL connections, causing client applications to fail and potentially resulting in data loss or transaction failures. Organizations using BIG-IP appliances for load balancing, application delivery, or SSL offloading may see significant operational disruption as the TMM restarts can affect multiple virtual servers and SSL profiles simultaneously.
Mitigation strategies for CVE-2019-6592 should prioritize immediate patching of affected systems to the latest available F5 BIG-IP releases that contain the security fix. Organizations should implement network monitoring to detect unusual TMM restart patterns or core file generation that may indicate exploitation attempts. Configuration controls should be established to limit SSL certificate validation complexity and implement certificate pre-validation processes to identify problematic certificates before they reach the TMM. Security teams should consider implementing intrusion detection systems that can monitor for patterns consistent with this vulnerability and establish incident response procedures for handling TMM restart events. Additionally, organizations should review their certificate management practices to ensure that certificates are properly validated and that certificate authorities are trusted sources to reduce the likelihood of encountering malformed certificates that could trigger this vulnerability. The fix addresses the underlying memory handling issue in the certificate validation routine and includes enhanced error handling to prevent the TMM from crashing during SSL certificate processing.