CVE-2017-7543: Race Condition
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.
Other sources
Paul Needle of Red Hat reports:
iptables/firewalld is not active on overcloud compute and controller nodes, following an 'openstack overcloud update ...' procedure run in a production environment yesterday. This has major impact given that there are end-customer workloads running in this environment.
— Red Hat
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
openstack-neutronto a version that resolves this vulnerability.Fixed in 7.2.0-12.1 - Upgrade
Upgrade
openstack-neutronto a version that resolves this vulnerability.Fixed in 8.3.0-11.1 - Upgrade
Upgrade
openstack-neutronto a version that resolves this vulnerability.Fixed in 9.3.1-2.1 - Upgrade
Upgrade
openstack-neutronto a version that resolves this vulnerability.Fixed in 10.0.2-1.1 - Configuration
Set net.bridge.bridge-nf-call-iptables back to a non-zero value after the overcloud minor update if it was reset to 0; the reported issue is that it was reset to 0 for neutron security groups to be disabled.
Linux kernel netfilter sysctl net.bridge.bridge-nf-call-iptables = 0 - Configuration
Set net.bridge.bridge-nf-call-ip6tables back to a non-zero value after the overcloud minor update if it was reset to 0; the reported issue is that it was reset to 0 for neutron security groups to be disabled.
Linux kernel netfilter sysctl net.bridge.bridge-nf-call-ip6tables = 0 - Compensating control
Because iptables/firewalld is not active on overcloud compute and controller nodes after the 'openstack overcloud update' procedure, enable/activate iptables or firewalld on those nodes to restore network filtering while remediation is applied.
Event History
Frequently Asked Questions
What is the severity of CVE-2017-7543?
CVE-2017-7543 is classified as a moderate severity vulnerability due to the risk of neutron security groups being disabled after an overcloud update.
How do I fix CVE-2017-7543?
To fix CVE-2017-7543, you should upgrade OpenStack Neutron to versions 7.2.0-12.1, 8.3.0-11.1, 9.3.1-2.1, or 10.0.2-1.1 or later.
Who is affected by CVE-2017-7543?
CVE-2017-7543 affects users of OpenStack Neutron versions prior to 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.
What specific issue does CVE-2017-7543 cause?
CVE-2017-7543 causes a race-condition flaw that can disable neutron security groups after a minor overcloud update.
Is there a workaround for CVE-2017-7543?
There are no specific workarounds for CVE-2017-7543; upgrading to a fixed version is the recommended course of action.