CVE-2018-5530 in BIG-IP
Summary
by MITRE
F5 BIG-IP 13.0.0-13.1.0.5, 12.1.0-12.1.3.5, or 11.6.0-11.6.3.1 virtual servers with HTTP/2 profiles enabled are vulnerable to "HPACK Bomb".
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Analysis
by VulDB Data Team • 04/25/2023
The CVE-2018-5530 vulnerability affects F5 BIG-IP load balancer appliances running specific versions with HTTP/2 profile configurations, presenting a critical security risk through an HPACK bomb attack. This vulnerability specifically targets the HTTP/2 implementation within the BIG-IP system's virtual servers, where the HTTP/2 profile is enabled, creating a potential denial of service condition that can severely impact network availability and application performance. The flaw exploits the HPACK compression algorithm used in HTTP/2 communications, which is designed to reduce bandwidth consumption by compressing HTTP headers. However, the vulnerability allows attackers to craft malicious HTTP/2 requests that can cause excessive memory consumption and processing overhead within the BIG-IP system, effectively leading to resource exhaustion and service disruption.
The technical implementation of this vulnerability stems from inadequate input validation and resource management within the HPACK decompression process. When an attacker sends specially crafted HTTP/2 requests with maliciously constructed header compression tables, the BIG-IP system attempts to decompress these headers using the HPACK algorithm without proper bounds checking or resource limitations. This allows an attacker to create a scenario where the system consumes excessive memory resources or CPU cycles, as the compression tables grow uncontrollably or the decompression process becomes computationally expensive. The vulnerability is particularly dangerous because it can be exploited with relatively simple requests that appear legitimate to the system's initial inspection, making detection and prevention challenging. This flaw aligns with CWE-400, which addresses "Uncontrolled Resource Consumption" and represents a classic example of a resource exhaustion attack that can be amplified through protocol-level weaknesses.
The operational impact of this vulnerability extends beyond simple denial of service conditions, potentially affecting critical business applications and services that rely on F5 BIG-IP appliances for load balancing and traffic management. Organizations utilizing affected BIG-IP versions with HTTP/2 profiles face significant risk of service interruptions, degraded performance, and potential data loss during attack scenarios. The vulnerability can be exploited remotely without authentication, making it particularly dangerous in environments where network exposure is high. Attackers can leverage this weakness to disrupt web applications, cause cascading failures in service availability, and potentially create conditions that allow for further exploitation of other system components. The impact is especially severe for organizations that depend heavily on HTTP/2 for performance optimization, as the vulnerability directly undermines the very protocol benefits that make HTTP/2 attractive for modern web applications.
Mitigation strategies for CVE-2018-5530 require immediate implementation of security patches provided by F5, which address the HPACK decompression logic and implement proper resource limits for header compression operations. Organizations should disable HTTP/2 profiles on affected virtual servers until patches are applied, or implement network-level controls such as rate limiting and connection throttling to prevent exploitation. The implementation of intrusion detection systems capable of identifying malformed HTTP/2 requests and monitoring for unusual resource consumption patterns provides additional defense layers. Security teams should also consider implementing application firewalls or web application firewalls that can filter out malicious HTTP/2 traffic before it reaches the BIG-IP appliances. According to ATT&CK framework, this vulnerability maps to T1499.004 for "Endpoint Termination: Network Denial of Service" and T1071.002 for "Application Layer Protocol: Web Protocols," indicating the need for defensive measures targeting both network-level and application-layer attacks. Regular vulnerability assessments and security monitoring should be implemented to detect similar weaknesses in other protocol implementations and ensure comprehensive protection against evolving attack vectors targeting modern web infrastructure components.