^{CVE-2019-18421:}An issue was discovered in Xen through 4.12.x allowing x86 PV guest OS users to gain host OS privileges by leveraging race conditions in pagetable promotion and demotion operations. There are issues with restartable PV type change operations. To avoid using shadow pagetables for PV guests, Xen exposes the actual hardware pagetables to the guest. In order to prevent the guest from modifying these page tables directly, Xen keeps track of how pages are used using a type system; pages must be "promoted" before being used as a pagetable, and "demoted" before being used for any other type. Xen also allows for "recursive" promotions: i.e., an operating system promoting a page to an L4 pagetable may end up causing pages to be promoted to L3s, which may in turn cause pages to be promoted to L2s, and so on. These operations may take an arbitrarily large amount of time, and so must be re-startable. Unfortunately, making recursive pagetable promotion and demotion operations restartable is incredibly complicated, and the code contains several races which, if triggered, can cause Xen to drop or retain extra type counts, potentially allowing guests to get write access to in-use pagetables. A malicious PV guest administrator may be able to escalate their privilege to that of the host. All x86 systems with untrusted PV guests are vulnerable. HVM and PVH guests cannot exercise this vulnerability.

Industry ExposureMost to least

This section illustrates the prevalence of a specific Common Vulnerabilities and Exposures (CVE) across various industries based on customer reports. The ranking displays industries from the most to least affected by this particular vulnerability, offering valuable insight into where this CVE has been most frequently observed. This information can help organizations within these sectors prioritize their security efforts, understand their relative risk exposure compared to their peers, and focus remediation strategies where they are most needed. By understanding the industry-specific impact, organizations can make more informed decisions regarding patching, resource allocation, and overall risk management related to this CVE.

1. Manufacturing
   Manufacturing
2. Finance and Insurance
   Finance and Insurance
3. Educational Services
   Educational Services
4. Professional, Scientific, & Technical Services
   Professional, Scientific, & Technical Services
5. Public Administration
   Public Administration
6. Retail Trade
   Retail Trade
7. Wholesale Trade
   Wholesale Trade
8. Accommodation & Food Services
   Accommodation & Food Services
9. Administrative, Support, Waste Management & Remediation Services
   Administrative, Support, Waste Management & Remediation Services
10. Agriculture, Forestry Fishing & Hunting
    Agriculture, Forestry Fishing & Hunting
11. Arts, Entertainment & Recreation
    Arts, Entertainment & Recreation
12. Construction
    Construction
13. Health Care & Social Assistance
    Health Care & Social Assistance
14. Information
    Information
15. Management of Companies & Enterprises
    Management of Companies & Enterprises
16. Mining
    Mining
17. Other Services (except Public Administration)
    Other Services (except Public Administration)
18. Real Estate Rental & Leasing
    Real Estate Rental & Leasing
19. Transportation & Warehousing
    Transportation & Warehousing
20. Utilities
    Utilities