FreeBSD-SA-18:06.debugreg Security Advisory
The FreeBSD Project
Topic: Mishandling of x86 debug exceptions
Credits: Nick Peterson, Everdox Tech LLC
https://www.linkedin.com/in/everdox Andy Lutomirski
Affects: All supported versions of FreeBSD.
Corrected: 2018-05-08 17:03:33 UTC (stable/11, 11.2-PRERELEASE)
2018-05-08 17:12:10 UTC (releng/11.1, 11.1-RELEASE-p10)
2018-05-08 17:05:39 UTC (stable/10, 10.4-STABLE)
2018-05-08 17:12:10 UTC (releng/10.4, 10.4-RELEASE-p9)
CVE Name: CVE-2018-8897
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/>.
On x86 architecture systems, the stack is represented by the combination of
a stack segment and a stack pointer, which must remain in sync for proper
operation. Instructions related to manipulating the stack segment have
special handling to facilitate consistency with changes to the stack pointer.
II. Problem Description
The MOV SS and POP SS instructions inhibit debug exceptions until the
instruction boundary following the next instruction. If that instruction is
a system call or similar instruction that transfers control to the operating
system, the debug exception will be handled in the kernel context instead of
the user context.
An authenticated local attacker may be able to read sensitive data in kernel
memory, control low-level operating system functions, or may panic the
No workaround is available.
Upgrade your vulnerable system to a supported FreeBSD stable or
release / security branch (releng) dated after the correction date,
using either a binary or source code patch, and then reboot.
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
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.