Vulnerability in Xen
CVE-2021-28705
issues with partially successful P2M updates on x86 T[his CNA information record relates to multiple CVEs; the text explains which aspects/vulnerabilities correspond to which CVE.] x86 HVM and PVH guests may be started in populate-on-demand (PoD) mode, to provide a way for them to later easily have more memory assigned. Guests are permitted to control certain P2M aspects of individual pages via hypercalls. These hypercalls may act on ranges of pages specified via page orders (resulting in a power-of-2 number of pages). In some cases the hypervisor carries out the requests by splitting them into smaller chunks. Error handling in certain PoD cases has been insufficient in that in particular partial success of some operations was not properly accounted for. There are two code paths affected - page removal (CVE-2021-28705) and insertion of new pages (CVE-2021-28709). (We provide one patch which combines the fix to both issues.)
EPSS: 0.003 (25.8th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 7.8 (High). Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H.
Affected products
- Xen — versions xen-unstable, 4.15.1, 4.15.0
- Debian Debian_linux — versions 11.0
- Fedoraproject Fedora — versions 34, 35
Weakness classification (CWE)
Public proof-of-concept exploits
References
- security@xen.org (Patch, Vendor Advisory)
- security@xen.org (vendor-advisory)
- security@xen.org (vendor-advisory, Third Party Advisory)
- security@xen.org (vendor-advisory)
- security@xen.org (vendor-advisory)
Frequently asked questions
- What is CVE-2021-28705?
- CVE-2021-28705 is a high-severity vulnerability in Xen, classified under Improper Handling of Exceptional Conditions. CVSS score: 7.8/10. Published 2021-11-24.
- How severe is CVE-2021-28705?
- High severity. CVSS v3 base score is 7.8 out of 10.
- Is CVE-2021-28705 known to be exploited?
- 1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.