CVE-2017-7518

A flaw was found in the Linux kernel before version 4.12 in the way the KVM module processed the trap flag(TF) bit in EFLAGS during emulation of the syscall instruction, which leads to a debug exception(#DB) being raised in the guest stack. A user/process inside a guest could use this flaw to potentially escalate their privileges inside the guest. Linux guests are not affected by this.

Weakness

The product performs an operation at a privilege level that is higher than the minimum level required, which creates new weaknesses or amplifies the consequences of other weaknesses.

Affected Software

Extended Description

New weaknesses can be exposed because running with extra privileges, such as root or Administrator, can disable the normal security checks being performed by the operating system or surrounding environment. Other pre-existing weaknesses can turn into security vulnerabilities if they occur while operating at raised privileges. Privilege management functions can behave in some less-than-obvious ways, and they have different quirks on different platforms. These inconsistencies are particularly pronounced if you are transitioning from one non-root user to another. Signal handlers and spawned processes run at the privilege of the owning process, so if a process is running as root when a signal fires or a sub-process is executed, the signal handler or sub-process will operate with root privileges.

Potential Mitigations

Related Attack Patterns

• https://cwe.mitre.org/data/definitions/104.html
• https://cwe.mitre.org/data/definitions/470.html
• https://cwe.mitre.org/data/definitions/69.html

References

• http://www.openwall.com/lists/oss-security/2017/06/23/5
• http://www.securityfocus.com/bid/99263
• http://www.securitytracker.com/id/1038782
• https://access.redhat.com/articles/3290921
• https://access.redhat.com/errata/RHSA-2018:0395
• https://access.redhat.com/errata/RHSA-2018:0412
• https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2017-7518
• https://usn.ubuntu.com/3619-1/
• https://usn.ubuntu.com/3619-2/
• https://usn.ubuntu.com/3754-1/
• https://www.debian.org/security/2017/dsa-3981
• https://www.spinics.net/lists/kvm/msg151817.html
• http://www.openwall.com/lists/oss-security/2017/06/23/5
• http://www.securityfocus.com/bid/99263
• http://www.securitytracker.com/id/1038782
• https://access.redhat.com/articles/3290921
• https://access.redhat.com/errata/RHSA-2018:0395
• https://access.redhat.com/errata/RHSA-2018:0412
• https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2017-7518
• https://usn.ubuntu.com/3619-1/
• https://usn.ubuntu.com/3619-2/
• https://usn.ubuntu.com/3754-1/
• https://www.debian.org/security/2017/dsa-3981
• https://www.spinics.net/lists/kvm/msg151817.html