CVE-2018-19115 in keepalived
Summary
by MITRE
keepalived through 2.0.8 has a heap-based buffer overflow when parsing HTTP status codes resulting in DoS or possibly unspecified other impact, because extract_status_code in lib/html.c has no validation of the status code and instead writes an unlimited amount of data to the heap.
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Analysis
by VulDB Data Team • 06/05/2023
The vulnerability identified as CVE-2018-19115 affects keepalived versions through 2.0.8 and represents a critical heap-based buffer overflow flaw that can lead to denial of service or potentially more severe consequences. This vulnerability exists within the HTTP status code parsing functionality of the keepalived load balancing and high availability software, which is widely deployed in production environments for ensuring service availability and failover capabilities. The issue stems from inadequate input validation within the extract_status_code function located in the lib/html.c source file, where the software fails to enforce bounds checking on status code data.
The technical implementation of this vulnerability demonstrates a classic buffer overflow condition where the application writes an unlimited amount of data to heap memory without proper validation of the status code length. When keepalived processes HTTP responses containing malformed or excessively long status codes, the extract_status_code function blindly accepts and writes this data to memory locations without checking whether the buffer size is sufficient to accommodate the incoming data. This lack of input validation creates a predictable memory corruption scenario that can be exploited by malicious actors who craft specially formatted HTTP responses designed to trigger the overflow condition.
The operational impact of CVE-2018-19115 extends beyond simple denial of service as the vulnerability can potentially lead to arbitrary code execution or system instability depending on how the heap corruption manifests. In production environments where keepalived serves as a critical component for load balancing and failover operations, this vulnerability can result in complete service disruption, making it particularly dangerous for organizations relying on high availability infrastructure. The vulnerability is especially concerning because it affects the core parsing functionality that handles HTTP monitoring, which is fundamental to keepalived's health checking mechanisms and service failover capabilities.
From a cybersecurity perspective, this vulnerability maps directly to CWE-121 heap-based buffer overflow and aligns with ATT&CK technique T1499.004 for network denial of service. The vulnerability represents a significant risk to operational security since it can be triggered through legitimate network traffic processing without requiring authentication or special privileges. Organizations using keepalived in their infrastructure should prioritize immediate patching of affected versions, as the vulnerability can be exploited remotely through crafted HTTP responses that the software processes during health checks. The exploitability of this vulnerability is high due to its location within the core monitoring functionality that processes external HTTP responses, making it a prime target for attackers seeking to disrupt service availability.
Mitigation strategies should include immediate deployment of patches for keepalived version 2.0.9 or later, which contain the necessary input validation fixes to prevent the buffer overflow condition. Network administrators should also implement monitoring for unusual HTTP response patterns that might indicate exploitation attempts, and consider implementing additional network segmentation to limit the impact of potential exploitation. The vulnerability serves as a reminder of the critical importance of input validation in security-critical applications, particularly in components that process external data streams such as health monitoring and load balancing functions. Organizations should conduct comprehensive vulnerability assessments of their keepalived deployments to ensure all instances are properly updated and monitored for similar issues in other components of their high availability infrastructure.