CVE-2012-2101 in Nova
Summary
by MITRE
Openstack Compute (Nova) Folsom, 2012.1, and 2011.3 does not limit the number of security group rules, which allows remote authenticated users with certain permissions to cause a denial of service (CPU and hard drive consumption) via a network request that triggers a large number of iptables rules.
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Analysis
by VulDB Data Team • 12/03/2021
The vulnerability identified as CVE-2012-2101 affects OpenStack Compute (Nova) versions Folsom, 2012.1, and 2011.3, representing a critical denial of service weakness that stems from inadequate enforcement of security group rule limits. This flaw exists within the Nova component responsible for managing virtual machine security groups, specifically in how it handles iptables rule creation and management. The vulnerability manifests when authenticated users with appropriate permissions submit network requests that generate an excessive number of iptables rules, leading to resource exhaustion and system instability.
The technical implementation of this vulnerability resides in the lack of validation and rate limiting mechanisms within Nova's security group handling code. When users create security groups with numerous rules, the system translates these into iptables entries without imposing reasonable limits on the total number of rules that can be applied to a single security group. This design flaw creates an environment where malicious or unauthorized users can exploit the system by submitting requests that trigger massive rule sets, causing iptables to consume excessive CPU cycles and disk I/O resources. The vulnerability is particularly dangerous because it requires only authenticated access with specific permissions, making it exploitable by users who already have some level of system access.
From an operational impact perspective, this vulnerability enables attackers to consume significant system resources through legitimate network requests, effectively creating a denial of service condition that can render the affected Nova services unavailable to legitimate users. The resource consumption manifests as high CPU utilization and disk space exhaustion, as each iptables rule requires system resources for processing and storage. This can lead to cascading failures where the system becomes unresponsive, affecting not only the specific service being targeted but potentially impacting the entire OpenStack deployment. The vulnerability's severity is amplified by its ability to be triggered through normal operational procedures, making it difficult to distinguish between legitimate and malicious requests.
The vulnerability aligns with CWE-770, which addresses allocation of resources without limits or with inadequate limits, and represents a classic example of resource exhaustion attack patterns. From the ATT&CK framework perspective, this vulnerability maps to T1499.004, which covers network denial of service attacks, and T1566.002, which involves spearphishing with social engineering. The attack vector requires network access and authentication, making it particularly concerning for cloud environments where multiple users share the same infrastructure. Organizations should implement strict rate limiting and rule count validation mechanisms to prevent excessive rule creation, while also establishing monitoring systems to detect unusual patterns of security group modifications that could indicate exploitation attempts. Additionally, regular security assessments and patch management processes should be enforced to ensure timely remediation of such vulnerabilities in cloud infrastructure deployments.