CVE-2019-6673 in BIG-IP
Summary
by MITRE
On versions 15.0.0-15.0.1 and 14.0.0-14.1.2, when the BIG-IP is configured in HTTP/2 Full Proxy mode, specifically crafted requests may cause a disruption of service provided by the Traffic Management Microkernel (TMM).
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Analysis
by VulDB Data Team • 03/05/2024
The vulnerability identified as CVE-2019-6673 represents a critical denial of service weakness within F5 Networks BIG-IP systems operating within HTTP/2 Full Proxy mode configurations. This flaw affects specific version ranges including 15.0.0 through 15.0.1 and 14.0.0 through 14.1.2, making it particularly concerning for organizations maintaining these system versions. The vulnerability manifests through specially crafted HTTP/2 requests that can disrupt service delivery by targeting the Traffic Management Microkernel component which serves as the core processing engine for traffic handling within BIG-IP appliances.
The technical implementation of this vulnerability stems from insufficient validation of HTTP/2 request parameters within the TMM processing pipeline. When the BIG-IP system processes these crafted requests in Full Proxy mode, the malformed data structures cause the TMM to enter an unstable state that ultimately results in service disruption. This behavior aligns with CWE-400 vulnerability classification, specifically addressing unchecked error conditions that can lead to resource exhaustion or system instability. The flaw essentially allows an attacker to exploit the HTTP/2 implementation to cause the system to consume excessive resources or enter a crash loop, effectively rendering the service unavailable to legitimate users.
The operational impact of this vulnerability extends beyond simple service disruption as it can affect critical infrastructure components that rely on BIG-IP load balancing and traffic management capabilities. Organizations utilizing HTTP/2 Full Proxy mode configurations face potential downtime that could span from minutes to hours depending on the recovery mechanisms implemented. The attack vector requires minimal sophistication as the malicious requests can be crafted using standard HTTP/2 tools and do not require authentication or elevated privileges. This makes the vulnerability particularly dangerous in production environments where continuous availability is paramount, and where the disruption can cascade across multiple dependent services that rely on the affected BIG-IP system.
Mitigation strategies for CVE-2019-6673 primarily focus on immediate version upgrades to patched releases of the BIG-IP software. F5 released security patches addressing this vulnerability in subsequent versions, making the most effective remediation the application of these updates. Organizations should also consider implementing temporary network-level controls such as rate limiting or request filtering to prevent malicious HTTP/2 traffic from reaching the vulnerable system. The ATT&CK framework categorizes this vulnerability under T1499.004 - Endpoint Denial of Service, specifically targeting network infrastructure components. Additionally, implementing proper monitoring and logging of HTTP/2 traffic patterns can help detect potential exploitation attempts, while network segmentation can limit the scope of impact if exploitation occurs. Organizations should also review their HTTP/2 configurations and consider disabling Full Proxy mode if the functionality is not strictly required, as this removes the attack surface entirely.