CVE-2020-5939

K75111593: BIG-IP VE network interface vulnerability CVE-2020-5939

Original Publication Date: Nov 03, 2020

Security Advisory Description

BIG-IP Virtual Edition (VE) systems on VMware, with an Intel-based 85299 Network Interface Controller (NIC) card and Single Root I/O Virtualization (SR-IOV) enabled on vSphere, may fail and leave the Traffic Management Microkernel (TMM) in a state where it cannot transmit traffic. (CVE-2020-5939)

Impact

TMM fails to process traffic, resulting in service disruption. If the affected BIG-IP system is configured as part of a device group, the system triggers a failover to the peer device.

Security Advisory Status

F5 Product Development has assigned ID 891457 (BIG-IP) to this vulnerability.

To determine if your product and version have been evaluated for this vulnerability, refer to the Applies to (see versions) box. To determine if your release is known to be vulnerable, the components or features that are affected by the vulnerability, and for information about releases, point releases, or hotfixes that address the vulnerability, refer to F5’s security advisory below. For more information about security advisory versioning, refer to K51812227: Understanding security advisory versioning.

Affected and fixed versions: F5 maintains the authoritative version matrix for this advisory, and it changes over time. For the current list of affected and fixed versions, see F5’s security advisory K75111593.

Security Advisory Recommended Actions

If you are running a version listed in the Versions known to be vulnerable column, you can eliminate this vulnerability by upgrading to a version listed in the Fixes introduced in column. If the table lists only an older version than what you are currently running, or does not list a non-vulnerable version, then no upgrade candidate currently exists.

Mitigation

To mitigate this vulnerability, you can disable TCP Segmentation Offload (TSO). You can do so by setting the value of the tm.tcpsegmentationoffload BigDB key to disable and restarting TMM. To do so, perform the following procedure:

Note

For more information about TSO, refer to K15609: Overview of TCP Segmentation Offload and Large Receive Offload.
Impact of action: The impact of the suggested mitigation depends on the specific environment. F5 recommends testing any such changes during a maintenance window with consideration to the possible impact on your specific environment. Additionally, restarting TMM temporarily interrupts traffic processing.

tmsh
2. Disable TSO by entering the following command:

modify sys db tm.tcpsegmentationoffload value disable
3. Restart TMM by entering the following command:

restart /sys service tmm