CVE-2017-7543 in openstack-neutron
Summary
by MITRE
A race-condition flaw was discovered in openstack-neutron before 7.2.0-12.1, 8.x before 8.3.0-11.1, 9.x before 9.3.1-2.1, and 10.x before 10.0.2-1.1, where, following a minor overcloud update, neutron security groups were disabled. Specifically, the following were reset to 0: net.bridge.bridge-nf-call-ip6tables and net.bridge.bridge-nf-call-iptables. The race was only triggered by an update, at which point an attacker could access exposed tenant VMs and network resources.
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Analysis
by VulDB Data Team • 11/10/2024
The vulnerability identified as CVE-2017-7543 represents a critical race condition flaw within the OpenStack Neutron networking service that affected multiple release versions prior to specific patch levels. This issue emerged from the complex interplay between network configuration management and update processes within OpenStack's cloud infrastructure. The flaw manifested specifically during minor overcloud updates, creating a window of opportunity where security group protections were temporarily disabled, leaving tenant virtual machines and network resources exposed to potential unauthorized access.
The technical nature of this vulnerability stems from improper synchronization during the update process of neutron security groups. When the system underwent a minor overcloud update, the race condition caused critical network bridge configuration parameters to be reset to zero values. Specifically, the parameters net.bridge.bridge-nf-call-ip6tables and net.bridge.bridge-nf-call-iptables were affected, which fundamentally disables the network filtering capabilities for both ipv6 and ipv4 traffic passing through the bridge. This reset operation occurred during the update sequence rather than being properly coordinated with the existing security policies, creating a temporal gap where network traffic was no longer properly filtered.
The operational impact of this vulnerability was severe and directly related to the fundamental security model of OpenStack cloud environments. During the brief window when these parameters were reset, tenant virtual machines became accessible to unauthorized network traffic that would normally be filtered by the security group policies. This exposure created a significant attack surface where malicious actors could potentially intercept communications, perform man-in-the-middle attacks, or gain unauthorized access to sensitive tenant data. The vulnerability was particularly dangerous because it occurred automatically during routine update operations, meaning that administrators were not actively triggering the condition but rather experiencing it as part of normal system maintenance.
The flaw aligns with CWE-362, which describes race conditions in software systems, and represents a classic example of improper resource management during concurrent operations. From an ATT&CK framework perspective, this vulnerability enables several techniques including privilege escalation through network access, lateral movement by accessing other tenant resources, and initial access by exploiting the temporary network filtering gaps. The vulnerability demonstrates how seemingly routine system maintenance operations can create security weaknesses when proper synchronization mechanisms are not implemented. Organizations using affected versions of OpenStack Neutron were particularly vulnerable because the race condition occurred automatically during update processes, making it difficult for administrators to predict or prevent the exposure window. The patching process required careful coordination of update procedures and proper synchronization of network configuration parameters to ensure that security group enforcement remained intact throughout the update lifecycle.