CVE-2017-6155 in BIG-IP
Summary
by MITRE
On F5 BIG-IP 13.0.0, 12.0.0-12.1.3.1, 11.6.0-11.6.2, 11.4.1-11.5.5, or 11.2.1, malformed SPDY or HTTP/2 requests may result in a disruption of service to TMM. Data plane is only exposed when a SPDY or HTTP/2 profile is attached to a virtual server. There is no control plane exposure.
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Analysis
by VulDB Data Team • 02/28/2023
The vulnerability identified as CVE-2017-6155 represents a critical denial of service flaw affecting F5 BIG-IP systems across multiple version ranges including 13.0.0, 12.0.0 through 12.1.3.1, 11.6.0 through 11.6.2, 11.4.1 through 11.5.5, and 11.2.1. This vulnerability specifically targets the Traffic Management Microkernel (TMM) component which handles the data plane processing of network traffic. The flaw manifests when the system receives malformed SPDY or HTTP/2 requests that are processed through virtual servers configured with SPDY or HTTP/2 profiles, creating a condition where legitimate service delivery becomes disrupted. The vulnerability operates exclusively within the data plane context, meaning that while the control plane remains unaffected, the operational impact on service availability can be severe and immediate.
The technical mechanism underlying this vulnerability involves the improper handling of malformed protocol frames within the SPDY and HTTP/2 request processing pipelines. When an attacker crafts specially malformed requests that exploit parsing inconsistencies in the TMM's handling of these protocols, the system experiences unexpected behavior that leads to service disruption. The vulnerability stems from insufficient input validation and error handling within the protocol parsing modules, allowing malformed data to cause the TMM to either crash or become unresponsive. This represents a classic example of a resource exhaustion or state corruption vulnerability that falls under the CWE-129 weakness category, specifically related to improper validation of array indices and protocol parsing errors. The attack vector requires the presence of a valid SPDY or HTTP/2 profile attached to a virtual server, making the exploitation dependent on specific configuration elements within the BIG-IP system.
The operational impact of this vulnerability extends beyond simple service interruption to potentially affect critical network infrastructure that relies on F5 BIG-IP appliances for load balancing and traffic management. Organizations utilizing these vulnerable versions may experience complete service disruption for applications served through affected virtual servers, leading to significant business impact and potential revenue loss. The vulnerability's exposure is limited to the data plane, meaning that while the control plane remains secure, the data plane disruption can cascade through the entire network infrastructure that depends on the affected BIG-IP appliance for traffic routing and load distribution. This characteristic makes the vulnerability particularly dangerous in environments where the BIG-IP serves as a core traffic management component, as the service disruption can affect multiple applications and services simultaneously. The ATT&CK framework categorizes this vulnerability under the T1498 technique for 'Network Denial of Service' and potentially T1071 for 'Application Layer Protocol' as it specifically targets protocol handling within application layer services.
Mitigation strategies for CVE-2017-6155 focus on immediate patching of affected systems to address the root cause in the protocol handling modules. Organizations should prioritize updating their F5 BIG-IP systems to versions that contain the necessary security patches, which typically include enhanced input validation and improved error handling for SPDY and HTTP/2 protocol parsing. Additionally, network administrators can implement temporary workarounds such as disabling SPDY or HTTP/2 profiles on virtual servers until the patches are applied, though this may impact performance and functionality for applications that specifically require these protocols. The implementation of rate limiting and connection monitoring can help detect and mitigate potential exploitation attempts, while network segmentation strategies can limit the impact scope of any successful attacks. Security teams should also monitor their systems for signs of exploitation attempts and maintain detailed logging of protocol handling activities to detect anomalous patterns that may indicate attempted exploitation of this vulnerability.