Privilege escalation in Xen
CVE-2021-28702
PCI devices with RMRRs not deassigned correctly Certain PCI devices in a system might be assigned Reserved Memory Regions (specified via Reserved Memory Region Reporting, "RMRR"). These are typically used for platform tasks such as legacy USB emulation. If such a device is passed through to a guest, then on guest shutdown the device is not properly deassigned. The IOMMU configuration for these devices which are not properly deassigned ends up pointing to a freed data structure, including the IO Pagetables. Subsequent DMA or interrupts from the device will have unpredictable behaviour, ranging from IOMMU faults to memory corruption.
Vulnerability class: Privilege Escalation
Published · last modified .
CVSS v3 metric
CVSS v3 base score 7.6 (High). Vector: CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H.
EPSS exploit prediction
EPSS: 0.004 (36.0th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 36th percentile — 36.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.004 · newest: 0.004 · change: 0.000
Affected products
- Xen — versions unspecified, 4.12.x, next of xen-unstable
- Debian Linux — versions 9.0
- Fedoraproject Fedora — versions 33, 34, 35
Weakness classification (CWE)
References
- xenbits.xenproject.org/xsa/advisory-386.txt (Vendor Advisory)
- www.openwall.com/lists/oss-security/2021/10/07/2 (mailing-list, Mailing List, Third Party Advisory)
- lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/… (vendor-advisory)
- lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/… (vendor-advisory)
- lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/… (vendor-advisory)
- www.debian.org/security/2021/dsa-5017 (vendor-advisory, Third Party Advisory)
- security.gentoo.org/glsa/202208-23 (vendor-advisory, Third Party Advisory)
Frequently asked questions
- What is CVE-2021-28702?
- CVE-2021-28702 is a high-severity vulnerability in Xen, classified under Improper Privilege Management. CVSS score: 7.6/10. Published 2021-10-06.
- How severe is CVE-2021-28702?
- High severity. CVSS v3 base score is 7.6 out of 10.