An issue was discovered in Open vSwitch (OvS) 2.7.x through 2.7.6, affecting parse_group_prop_ntr_selection_method in lib/ofp-util.c. When decoding a group mod, it validates the group type and command after the whole group mod has been decoded. The OF1.5 decoder, however, tries to use the type and command earlier, when it might still be invalid. This causes an assertion failure (via OVS_NOT_REACHED). ovs-vswitchd does not enable support for OpenFlow 1.5 by default.
The product contains an assert() or similar statement that can be triggered by an attacker, which leads to an application exit or other behavior that is more severe than necessary.
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Openvswitch | Openvswitch | 2.7.0 (including) | 2.7.6 (including) |
| Fast Datapath for Red Hat Enterprise Linux 7 | RedHat | openvswitch-0:2.9.0-70.el7fdp.1 | * |
| Red Hat OpenStack Platform 10.0 (Newton) | RedHat | openvswitch-0:2.9.0-83.el7fdp.1 | * |
| Red Hat OpenStack Platform 13.0 (Queens) | RedHat | openvswitch-0:2.9.0-83.el7fdp.1 | * |
| Red Hat Virtualization 4.2 for Red Hat Enterprise Linux 7.6 EUS | RedHat | openvswitch-0:2.9.0-70.el7fdp.1 | * |
| Red Hat Virtualization 4 for Red Hat Enterprise Linux 7 | RedHat | redhat-release-virtualization-host-0:4.2-7.5.el7 | * |
| Red Hat Virtualization 4 for Red Hat Enterprise Linux 7 | RedHat | redhat-virtualization-host-0:4.2-20181121.0.el7_6 | * |
| Openvswitch | Ubuntu | bionic | * |
| Openvswitch | Ubuntu | xenial | * |
While assertion is good for catching logic errors and reducing the chances of reaching more serious vulnerability conditions, it can still lead to a denial of service. For example, if a server handles multiple simultaneous connections, and an assert() occurs in one single connection that causes all other connections to be dropped, this is a reachable assertion that leads to a denial of service.