FreeBSD-SA-20:17.usb Security Advisory
The FreeBSD Project
Topic: USB HID descriptor parsing error
Credits: Andy Nguyen, Google
Affects: All supported versions of FreeBSD.
Corrected: 2020-06-08 09:32:57 UTC (stable/12, 12.1-STABLE)
2020-06-09 16:13:54 UTC (releng/12.1, 12.1-RELEASE-p6)
2020-06-08 09:33:37 UTC (stable/11, 11.4-STABLE)
2020-06-09 16:13:54 UTC (releng/11.4, 11.4-RC2-p1)
2020-06-09 16:13:54 UTC (releng/11.3, 11.3-RELEASE-p10)
CVE Name: CVE-2020-7456
For general information regarding FreeBSD Security Advisories,
including descriptions of the fields above, security branches, and the
following sections, please visit <URL:https://security.FreeBSD.org/>.
USB Human Interface Device (HID) descriptors may push/pop the current state
to allow description of items residing in a so-called union. FreeBSD
supports 4 such pop levels.
II. Problem Description
If the push/pop level is not restored within the processing of the same HID
item, an invalid memory location may be used for subsequent HID item
An attacker with physical access to a USB port may be able to use a specially
crafted USB device to gain kernel or user-space code execution.
Setting "sysctl hw.usb.disable_enumeration=1" disables USB device
enumeration preventing the error from occurring.
Upgrade your vulnerable system to a supported FreeBSD stable or
release / security branch (releng) dated after the correction date,
Perform one of the following:
1) To update your vulnerable system via a binary patch:
Systems running a RELEASE version of FreeBSD on the i386 or amd64
platforms can be updated via the freebsd-update(8) utility:
# freebsd-update fetch
# freebsd-update install
# shutdown -r +10min "Rebooting for a security update"
2) To update your vulnerable system via a source code patch:
The following patches have been verified to apply to the applicable
FreeBSD release branches.
a) Download the relevant patch from the location below, and verify the
detached PGP signature using your PGP utility.