CVE-2021-3308
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.
Does this matter?
Lower severity and a low EPSS score (0.42%). Track it; it rarely justifies an emergency change on its own.
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.
- CVSS 3.1
- 5.5 MEDIUMCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
- EPSS
- 0.42% probability · 36th percentile
- Public exploits
- None in Exploit-DB
- CISA KEV
- Not listed
- Affected
- xen/xen · fedoraproject/fedora
- Source
- cve@mitre.org
EPSS 0.4% since 26 October 2026; no change recorded yet. Points are recorded when the score first appears and whenever it moves by a percentage point or more.
References
- http://www.openwall.com/lists/oss-security/2021/01/26/4Mailing List, Patch, Third Party Advisory
- http://xenbits.xen.org/xsa/advisory-360.htmlPatch, Vendor Advisory
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/S5C42TMQYB6SDVT2MPFEWY65A6RSUVBN/
- https://security.gentoo.org/glsa/202107-30Third Party Advisory
- http://www.openwall.com/lists/oss-security/2021/01/26/4Mailing List, Patch, Third Party Advisory
- http://xenbits.xen.org/xsa/advisory-360.htmlPatch, Vendor Advisory
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/S5C42TMQYB6SDVT2MPFEWY65A6RSUVBN/
- https://security.gentoo.org/glsa/202107-30Third Party Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.