An issue was discovered in Xen through 4.11.x. The DEBUGCTL MSR contains several debugging features, some of which virtualise cleanly, but some do not. In particular, Branch Trace Store is not virtualised by the processor, and software has to be careful to configure it suitably not to lock up the core. As a result, it must only be available to fully trusted guests. Unfortunately, in the case that vPMU is disabled, all value checking was skipped, allowing the guest to choose any MSR_DEBUGCTL setting it likes. A malicious or buggy guest administrator (on Intel x86 HVM or PVH) can lock up the entire host, causing a Denial of Service.
The MITRE CVE dictionary describes this issue as:
Find out more about CVE-2018-15468 from the MITRE CVE dictionary dictionary and NIST NVD.
NOTE: The following CVSS v3 metrics and score provided are preliminary and subject to review.
| CVSS3 Base Score | 6 |
|---|---|
| CVSS3 Base Metrics | CVSS:3.0/AV:L/AC:L/PR:H/UI:N/S:C/C:N/I:N/A:H |
| Attack Vector | Local |
| Attack Complexity | Low |
| Privileges Required | High |
| User Interaction | None |
| Scope | Changed |
| Confidentiality | None |
| Integrity Impact | None |
| Availability Impact | High |
| Platform | Package | State |
|---|---|---|
| Red Hat Enterprise Linux 5 | xen | Not affected |
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