CVE-2014-3517 in Compute
Summary
by MITRE
api/metadata/handler.py in OpenStack Compute (Nova) before 2013.2.4, 2014.x before 2014.1.2, and Juno before Juno-2, when proxying metadata requests through Neutron, makes it easier for remote attackers to guess instance ID signatures via a brute-force attack that relies on timing differences in responses to instance metadata requests.
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Analysis
by VulDB Data Team • 03/26/2022
The vulnerability described in CVE-2014-3517 resides within the OpenStack Compute (Nova) component, specifically in the api/metadata/handler.py file, which handles metadata requests for virtual instances. This flaw affects multiple versions of OpenStack including the 2013.2.4 release and earlier versions of the 2014.x series up to 2014.1.1, as well as the Juno release series before Juno-2. The vulnerability manifests when the system proxies metadata requests through the Neutron networking service, creating a significant security risk that impacts the confidentiality and integrity of virtual machine instances within OpenStack deployments.
The technical flaw stems from the implementation of metadata request handling that exhibits timing variations in response processing for different instance ID signatures. When remote attackers make metadata requests to the Nova service, the system's response time varies depending on whether the requested instance ID exists or not. This timing difference creates a side-channel attack vector that allows malicious actors to perform brute-force attacks against instance ID signatures. The vulnerability specifically exploits the differential response times between valid and invalid instance ID lookups, enabling attackers to systematically guess valid instance IDs through repeated requests and timing analysis.
The operational impact of this vulnerability is substantial as it directly compromises the security of virtual machine instances within OpenStack cloud environments. Attackers can leverage this timing-based information leakage to discover valid instance IDs, which serves as a critical first step in potential compromise scenarios. Once valid instance IDs are obtained, attackers can proceed with further exploitation attempts including but not limited to metadata manipulation, instance enumeration, and potentially gaining unauthorized access to sensitive instance data. The vulnerability essentially undermines the fundamental security assumptions of instance isolation within virtualized environments, making it easier for adversaries to target specific virtual machines within a cloud deployment.
This vulnerability aligns with CWE-203, which describes "Information Exposure Through Timing Discrepancy," and represents a classic example of how seemingly innocuous implementation details can create significant security weaknesses. The attack pattern follows the techniques documented in MITRE ATT&CK framework under T1083 (File and Directory Discovery) and T1566 (Phishing for Information) as attackers can systematically enumerate instance metadata to gather intelligence. The timing side-channel attack vector is particularly concerning because it requires minimal privileges and can be executed remotely without direct access to the underlying infrastructure, making it an attractive target for attackers seeking to compromise cloud environments.
Organizations should implement immediate mitigations including updating to patched versions of OpenStack Nova where the timing discrepancies have been eliminated through consistent response handling. The fix typically involves ensuring that all metadata requests, whether for valid or invalid instance IDs, return responses with consistent timing characteristics to prevent the side-channel information leakage. Additionally, administrators should consider implementing rate limiting and access controls for metadata services, while monitoring for unusual patterns of metadata requests that might indicate brute-force attempts. Network-level protections such as firewall rules that limit access to metadata endpoints and the implementation of additional authentication layers can provide defense-in-depth measures. Regular security assessments and penetration testing of cloud environments should include verification that timing-based vulnerabilities have been properly addressed to ensure comprehensive protection against similar information disclosure threats.