CVE-2018-12891
First published: Mon Jul 02 2018(Updated: )
An issue was discovered in Xen through 4.10.x. Certain PV MMU operations may take a long time to process. For that reason Xen explicitly checks for the need to preempt the current vCPU at certain points. A few rarely taken code paths did bypass such checks. By suitably enforcing the conditions through its own page table contents, a malicious guest may cause such bypasses to be used for an unbounded number of iterations. A malicious or buggy PV guest may cause a Denial of Service (DoS) affecting the entire host. Specifically, it may prevent use of a physical CPU for an indeterminate period of time. All Xen versions from 3.4 onwards are vulnerable. Xen versions 3.3 and earlier are vulnerable to an even wider class of attacks, due to them lacking preemption checks altogether in the affected code paths. Only x86 systems are affected. ARM systems are not affected. Only multi-vCPU x86 PV guests can leverage the vulnerability. x86 HVM or PVH guests as well as x86 single-vCPU PV ones cannot leverage the vulnerability.
Credit: cve@mitre.org
| Affected Software | Affected Version | How to fix |
|---|---|---|
| debian/xen | 4.11.4+107-gef32c7afa2-1 4.14.6-1 4.14.5+94-ge49571868d-1 4.17.1+2-gb773c48e36-1 4.17.2+55-g0b56bed864-1 | |
| Debian GNU/Linux | =8.0 | |
| Debian GNU/Linux | =9.0 | |
| Xen xen-unstable | <=4.10.1 |
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Reference Links
- http://www.openwall.com/lists/oss-security/2018/06/27/10
- http://www.securityfocus.com/bid/104570
- http://www.securitytracker.com/id/1041201
- http://xenbits.xen.org/xsa/advisory-264.html
- https://lists.debian.org/debian-lts-announce/2018/11/msg00013.html
- https://security.gentoo.org/glsa/201810-06
- https://support.citrix.com/article/CTX235748
- https://www.debian.org/security/2018/dsa-4236
- https://xenbits.xen.org/xsa/advisory-264.html
- https://security-tracker.debian.org/tracker/CVE-2018-12891
Frequently Asked Questions
What is the severity of CVE-2018-12891?
CVE-2018-12891 is classified as a medium severity vulnerability due to performance impacts on virtual machine operations.
How do I fix CVE-2018-12891?
To fix CVE-2018-12891, update to Xen versions 4.11.4+107-gef32c7afa2-1, 4.14.6-1, or later versions.
What types of software are affected by CVE-2018-12891?
CVE-2018-12891 affects Xen versions up to 4.10.1 and Debian GNU/Linux versions 8.0 and 9.0.
What are the potential impacts of CVE-2018-12891?
The potential impacts of CVE-2018-12891 include performance degradation and delayed responses from virtual machines.
Is CVE-2018-12891 a remote vulnerability?
CVE-2018-12891 is not a remote vulnerability; it requires access to the Xen hypervisor environment.
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