CVE-2019-10153 in fence-agents
Summary
by MITRE
A flaw was discovered in fence-agents, prior to version 4.3.4, where using non-ASCII characters in a guest VM's comment or other fields would cause fence_rhevm to exit with an exception. In cluster environments, this could lead to preventing automated recovery or otherwise denying service to clusters of which that VM is a member.
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Analysis
by VulDB Data Team • 11/14/2023
The vulnerability identified as CVE-2019-10153 represents a critical input handling flaw within the fence-agents framework, specifically affecting the fence_rhevm component used in Red Hat Enterprise Virtualization environments. This issue manifests when non-ASCII characters are present in guest VM comments or other metadata fields, causing the fencing agent to terminate abruptly with an exception rather than gracefully handling the unexpected character encoding. The flaw exists in versions prior to 4.3.4 and demonstrates a fundamental weakness in the agent's ability to process internationalized text input that is commonly encountered in enterprise virtualization deployments where localized naming conventions and descriptive text are standard practice.
The technical root cause of this vulnerability stems from inadequate character encoding validation and exception handling within the fence_rhevm implementation. When the agent encounters non-ASCII characters in VM metadata fields, the parsing logic fails to properly convert or sanitize the input before processing, resulting in a runtime exception that terminates the fencing operation. This behavior directly violates the principle of robust error handling and input validation that should be implemented in security-critical components. The vulnerability maps to CWE-170, which specifically addresses improper handling of input that could cause a program to fail or behave unexpectedly, and demonstrates poor adherence to secure coding practices that are essential for maintaining system availability and reliability in clustered environments.
The operational impact of this vulnerability extends beyond simple functional failure to pose significant risks to cluster availability and disaster recovery operations. In clustered virtualization environments, the fence_rhevm agent serves as a critical component for ensuring proper VM fencing and failover procedures during system failures or maintenance events. When the agent crashes due to non-ASCII characters in VM metadata, it prevents automated recovery mechanisms from functioning correctly, potentially leading to extended downtime and service disruption. This creates a denial of service condition that can affect multiple VMs within a cluster simultaneously, particularly when the problematic VMs are members of critical services or applications that depend on automated failover capabilities. The vulnerability essentially creates a single point of failure that can cascade throughout the entire cluster infrastructure, making it particularly dangerous in mission-critical environments where high availability is paramount.
Organizations affected by this vulnerability should prioritize immediate patching to version 4.3.4 or later, which contains the necessary input validation and encoding handling improvements. System administrators should conduct thorough inventory checks to identify all VMs with non-ASCII characters in their metadata fields and consider implementing automated remediation procedures to sanitize these fields before applying the patch. Additionally, monitoring should be implemented to detect similar encoding issues in other fence-agents components that may exhibit similar vulnerabilities. The mitigation strategy should also include regular security assessments of virtualization management components to identify potential encoding-related vulnerabilities that could impact cluster availability. Organizations should consider implementing input sanitization policies at the virtualization management layer to prevent non-ASCII characters from being introduced into critical metadata fields, thereby reducing the attack surface for similar vulnerabilities. This vulnerability underscores the importance of comprehensive testing procedures that include international character sets and proper exception handling in security-critical infrastructure components, aligning with ATT&CK technique T1499.004 for ensuring system availability and preventing service disruption through proper input validation and error handling mechanisms.