CVE-2013-4469 in Folsom
Summary
by MITRE
OpenStack Compute (Nova) Folsom, Grizzly, and Havana, when use_cow_images is set to False, does not verify the virtual size of a QCOW2 image, which allows local users to cause a denial of service (host file system disk consumption) by transferring an image with a large virtual size that does not contain a large amount of data from Glance. NOTE: this issue is due to an incomplete fix for CVE-2013-2096.
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Analysis
by VulDB Data Team • 01/10/2022
The vulnerability described in CVE-2013-4469 represents a significant security flaw within OpenStack Compute (Nova) versions Folsom, Grizzly, and Havana. This issue specifically manifests when the use_cow_images configuration parameter is set to False, creating a condition where the system fails to properly validate the virtual size of QCOW2 disk images. The flaw stems from an incomplete remediation of CVE-2013-2096, indicating that the initial fix was insufficient to address all potential attack vectors within the image handling process. This oversight creates a critical gap in the system's image validation mechanisms, particularly affecting how virtual disk images are processed and stored within the cloud infrastructure.
The technical nature of this vulnerability involves a mismatch between the reported virtual size of QCOW2 images and their actual data content. When a QCOW2 image is uploaded through Glance with a large virtual size but minimal actual data, the system does not perform adequate verification to ensure that the image's virtual capacity aligns with its physical storage requirements. This discrepancy allows malicious actors to exploit the system by uploading specially crafted images that appear to be large virtual disks but contain only small amounts of actual data. The system allocates disk space based on the reported virtual size rather than the actual data content, leading to inefficient storage utilization and potential resource exhaustion.
The operational impact of this vulnerability extends beyond simple resource waste to encompass serious denial of service conditions that can compromise entire host file systems. Local users can exploit this flaw to consume excessive disk space on the host system, potentially leading to complete system outages when storage capacity is exhausted. The vulnerability specifically targets the host file system disk consumption, meaning that attackers can fill up available storage space on the compute nodes where Nova instances are running. This type of attack can be particularly devastating in cloud environments where multiple tenants share the same physical infrastructure, as it can affect not only the attacking user's resources but potentially impact other users and system stability.
From a cybersecurity perspective, this vulnerability aligns with several established frameworks and threat models. The issue demonstrates characteristics consistent with CWE-128, which deals with Buffer Overflow conditions, and CWE-400, which addresses Uncontrolled Resource Consumption. The vulnerability also maps to ATT&CK techniques related to resource exhaustion and denial of service attacks, specifically targeting the system's storage management capabilities. The incomplete fix for CVE-2013-2096 suggests a pattern of security issues where remediation efforts fail to address all potential attack surfaces, highlighting the importance of comprehensive vulnerability assessment and testing.
Mitigation strategies for CVE-2013-4469 should focus on implementing proper image validation mechanisms that verify both the virtual and actual size of QCOW2 images before storage allocation occurs. Organizations should consider enabling the use_cow_images parameter when possible, as this setting provides additional protective layers against such attacks. The recommended approach involves implementing strict image size validation checks that ensure the virtual size of images corresponds appropriately with their actual data content. Additionally, system administrators should monitor storage utilization patterns and implement automated alerts when disk space consumption exceeds normal thresholds. The fix should also include proper input validation and sanitization of image metadata to prevent maliciously crafted virtual sizes from being accepted by the system. Regular security auditing and penetration testing of cloud infrastructure components can help identify similar incomplete fixes that may exist in other areas of the OpenStack deployment, ensuring comprehensive protection against resource exhaustion attacks that could compromise system availability and stability.