Privilege escalation in Xen
CVE-2021-28710
certain VT-d IOMMUs may not work in shared page table mode For efficiency reasons, address translation control structures (page tables) may (and, on suitable hardware, by default will) be shared between CPUs, for second-level translation (EPT), and IOMMUs. These page tables are presently set up to always be 4 levels deep. However, an IOMMU may require the use of just 3 page table levels. In such a configuration the lop level table needs to be stripped before inserting the root table's address into the hardware pagetable base register. When sharing page tables, Xen erroneously skipped this stripping. Consequently, the guest is able to write to leaf page table entries.
Vulnerability class: Privilege Escalation
EPSS: 0.003 (19.8th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 8.8 (High). Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H.
Affected products
- Xen — versions unspecified, next of xen-unstable, 4.15.0
- Fedoraproject Fedora — versions 35
Weakness classification (CWE)
References
- security@xen.org (x_refsource_MISC, Vendor Advisory)
- security@xen.org (x_refsource_FEDORA, vendor-advisory)
- security@xen.org (vendor-advisory, Third Party Advisory, x_refsource_GENTOO)
Frequently asked questions
- What is CVE-2021-28710?
- CVE-2021-28710 is a high-severity vulnerability in Xen, classified under Improper Privilege Management. CVSS score: 8.8/10. Published 2021-11-21.
- How severe is CVE-2021-28710?
- High severity. CVSS v3 base score is 8.8 out of 10.