CVE-2015-7713 in Compute
Summary
by MITRE
OpenStack Compute (Nova) before 2014.2.4 (juno) and 2015.1.x before 2015.1.2 (kilo) do not properly apply security group changes, which allows remote attackers to bypass intended restriction by leveraging an instance that was running when the change was made.
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Analysis
by VulDB Data Team • 06/25/2022
OpenStack Compute (Nova) versions prior to 2014.2.4 and 2015.1.2 contained a critical security vulnerability that fundamentally compromised the integrity of network access controls within cloud environments. This vulnerability specifically affected the implementation of security groups, which are essential components for controlling network traffic to and from virtual machine instances. The flaw manifested in the improper application of security group changes, creating a persistent bypass mechanism that allowed unauthorized network access to running instances.
The technical nature of this vulnerability stems from a failure in Nova's security group management system to properly refresh or apply updated security group rules to existing running instances. When security group modifications were made to a running instance, the system failed to immediately enforce these changes, leaving the instance vulnerable to network traffic that should have been blocked by the updated rules. This represents a direct violation of the principle of least privilege and undermines the fundamental security model of cloud computing environments where network isolation is paramount for multi-tenant security.
The operational impact of CVE-2015-7713 was severe and far-reaching across OpenStack deployments. Remote attackers could exploit this vulnerability to gain unauthorized access to virtual machines that were already running when security group changes occurred. This meant that even if administrators had properly configured security groups to restrict access, running instances would continue to accept traffic according to their original configuration, effectively bypassing the intended network restrictions. The vulnerability created a window of opportunity for attackers to establish persistence, exfiltrate data, or escalate privileges within compromised instances.
This vulnerability aligns with CWE-284, which addresses improper access control, and specifically relates to the failure to properly enforce access restrictions in a cloud computing environment. The attack pattern follows the MITRE ATT&CK framework's technique T1071.001 for Application Layer Protocol: Web Protocols, where attackers can exploit network access control mechanisms to bypass security boundaries. Organizations using affected OpenStack versions faced significant risk of data breaches, unauthorized access to sensitive resources, and potential compromise of entire cloud deployments. The vulnerability's persistence across multiple release branches indicated a systemic issue in Nova's security group implementation that required immediate patching and remediation across affected deployments.
The fix for CVE-2015-7713 involved implementing proper refresh mechanisms for security group rules on running instances and ensuring that all security group changes were immediately applied to existing virtual machines. Organizations were advised to upgrade to the patched versions of OpenStack Nova to mitigate the risk of unauthorized network access and maintain proper cloud security boundaries. This vulnerability highlighted the critical importance of proper access control enforcement in cloud environments and demonstrated how seemingly minor implementation flaws could have significant security implications for multi-tenant cloud deployments.