CVE-2015-7548 in Compute
Summary
by MITRE
OpenStack Compute (Nova) before 2015.1.3 (kilo) and 12.0.x before 12.0.1 (liberty), when using libvirt to spawn instances and use_cow_images is set to false, allow remote authenticated users to read arbitrary files by overwriting an instance disk with a crafted image and requesting a snapshot.
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Analysis
by VulDB Data Team • 07/02/2022
The vulnerability identified as CVE-2015-7548 represents a critical security flaw in OpenStack Compute (Nova) that emerged in versions prior to 2015.1.3 (kilo) and 12.0.1 (liberty). This issue specifically affects cloud environments utilizing libvirt for instance management and where the configuration parameter use_cow_images is set to false. The vulnerability stems from insufficient validation mechanisms during the instance disk handling process, creating a path for authenticated attackers to exploit file read privileges beyond their intended scope.
The technical implementation of this vulnerability involves a sophisticated manipulation of virtual machine disk images through crafted malicious input. When an attacker with valid credentials creates or modifies an instance disk image, they can overwrite the target disk with a specially constructed image file. This manipulation allows the attacker to subsequently request a snapshot operation that inadvertently exposes the contents of arbitrary files on the underlying system. The flaw operates through the libvirt hypervisor interface where the system fails to properly validate or sanitize the disk image content before processing snapshot requests. This vulnerability aligns with CWE-22, which addresses improper limitation of a pathname to a restricted directory, and CWE-20, which covers improper input validation, both of which are fundamental security principles in software development.
The operational impact of CVE-2015-7548 extends beyond simple data theft, as it provides attackers with the capability to access sensitive system information, configuration files, and potentially credentials stored on the host system. The vulnerability affects organizations running OpenStack deployments where multiple tenants share the same infrastructure, as the malicious user can potentially read files belonging to other tenants or system administrators. This creates a significant risk for cloud service providers who must ensure proper isolation between tenant environments, representing a direct violation of the principle of least privilege. The attack vector requires only authenticated access, making it particularly dangerous in environments where user accounts are widely distributed or where account compromise is possible through other means.
From a threat modeling perspective, this vulnerability maps directly to several ATT&CK techniques including T1005 (Data from Local System) and T1059 (Command and Scripting Interpreter) as attackers can leverage the file read capabilities to gather system information and potentially escalate privileges. The vulnerability also intersects with T1566 (Phishing) as attackers might use the information gathered to craft more sophisticated social engineering attacks or to identify additional system weaknesses. Organizations should implement immediate mitigations including updating to patched versions of Nova, disabling the use_cow_images configuration parameter when not required, and implementing strict access controls and monitoring for snapshot operations. Additionally, network segmentation and least privilege access models should be enforced to limit the potential impact of successful exploitation, as the vulnerability requires authenticated access but can potentially provide extensive system information disclosure.