CVE-2012-3371 in Compute
Summary
by MITRE
The Nova scheduler in OpenStack Compute (Nova) Folsom (2012.2) and Essex (2012.1), when DifferentHostFilter or SameHostFilter is enabled, allows remote authenticated users to cause a denial of service (excessive database lookup calls and server hang) via a request with many repeated IDs in the os:scheduler_hints section.
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Analysis
by VulDB Data Team • 12/06/2021
The vulnerability identified as CVE-2012-3371 represents a critical denial of service weakness within the Nova scheduler component of OpenStack Compute platforms. This flaw specifically affects the Folsom (2012.2) and Essex (2012.1) releases where the scheduler employs either the DifferentHostFilter or SameHostFilter mechanisms. The vulnerability stems from insufficient input validation and sanitization within the scheduler's handling of scheduler hints, creating a condition where maliciously crafted requests can trigger excessive resource consumption. The issue manifests when authenticated users submit requests containing numerous repeated identifiers within the os:scheduler_hints section, leading to cascading database lookup operations that can overwhelm system resources.
The technical implementation of this vulnerability exploits the scheduler's filtering mechanisms by leveraging the way these filters process host hint data. When DifferentHostFilter or SameHostFilter is enabled, the system iterates through the provided host identifiers to determine appropriate scheduling decisions. The flaw occurs because the scheduler does not adequately limit or deduplicate the repeated IDs in the scheduler hints, causing the system to perform redundant database queries for each occurrence of the same identifier. This results in exponential growth of database operations that can quickly exhaust available connections and processing capacity. The vulnerability is classified under CWE-400 as an Uncontrolled Resource Consumption issue, specifically manifesting as a resource exhaustion attack that targets the database layer.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise the entire OpenStack deployment's stability and availability. When exploited, the excessive database lookups can cause the Nova scheduler to become unresponsive, leading to server hangs that affect the scheduling of new instances and the management of existing virtual machines. This creates a cascading effect where legitimate users experience delays or complete inability to provision compute resources. The attack requires only authenticated access to the system, making it particularly dangerous as it can be exploited by users with minimal privileges who have access to the OpenStack API. According to ATT&CK framework category T1499, this vulnerability represents a Resource Exhaustion technique that targets system services to deny legitimate use.
Mitigation strategies for CVE-2012-3371 should focus on implementing input validation and rate limiting mechanisms within the Nova scheduler component. The primary recommendation involves configuring proper bounds checking on the number of scheduler hint entries allowed in a single request, combined with deduplication logic to eliminate redundant host identifiers before processing. Organizations should also implement database connection pooling limits and query timeout mechanisms to prevent complete system hangs. Updates to newer versions of OpenStack Nova that have addressed this vulnerability through improved filtering logic and input sanitization represent the most effective long-term solution. Additionally, monitoring systems should be configured to detect unusual patterns of database queries that could indicate exploitation attempts, providing early warning capabilities for administrators to respond to potential attacks.