CVE-2018-1087

kernel KVM before versions kernel 4.16, kernel 4.16-rc7, kernel 4.17-rc1, kernel 4.17-rc2 and kernel 4.17-rc3 is vulnerable to a flaw in the way the Linux kernels KVM hypervisor handled exceptions delivered after a stack switch operation via Mov SS or Pop SS instructions. During the stack switch operation, the processor did not deliver interrupts and exceptions, rather they are delivered once the first instruction after the stack switch is executed. An unprivileged KVM guest user could use this flaw to crash the guest or, potentially, escalate their privileges in the guest.

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/2018/05/08/5
• http://www.securityfocus.com/bid/104127
• http://www.securitytracker.com/id/1040862
• https://access.redhat.com/errata/RHSA-2018:1318
• https://access.redhat.com/errata/RHSA-2018:1345
• https://access.redhat.com/errata/RHSA-2018:1347
• https://access.redhat.com/errata/RHSA-2018:1348
• https://access.redhat.com/errata/RHSA-2018:1355
• https://access.redhat.com/errata/RHSA-2018:1524
• https://access.redhat.com/security/vulnerabilities/pop_ss
• https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2018-1087
• https://usn.ubuntu.com/3641-1/
• https://usn.ubuntu.com/3641-2/
• https://www.debian.org/security/2018/dsa-4196
• http://www.openwall.com/lists/oss-security/2018/05/08/5
• http://www.securityfocus.com/bid/104127
• http://www.securitytracker.com/id/1040862
• https://access.redhat.com/errata/RHSA-2018:1318
• https://access.redhat.com/errata/RHSA-2018:1345
• https://access.redhat.com/errata/RHSA-2018:1347
• https://access.redhat.com/errata/RHSA-2018:1348
• https://access.redhat.com/errata/RHSA-2018:1355
• https://access.redhat.com/errata/RHSA-2018:1524
• https://access.redhat.com/security/vulnerabilities/pop_ss
• https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2018-1087
• https://usn.ubuntu.com/3641-1/
• https://usn.ubuntu.com/3641-2/
• https://www.debian.org/security/2018/dsa-4196