CVE-2021-28707
First published: Wed Nov 24 2021(Updated: )
PoD operations on misaligned GFNs 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). The implementation of some of these hypercalls for PoD does not enforce the base page frame number to be suitably aligned for the specified order, yet some code involved in PoD handling actually makes such an assumption. These operations are XENMEM_decrease_reservation (CVE-2021-28704) and XENMEM_populate_physmap (CVE-2021-28707), the latter usable only by domains controlling the guest, i.e. a de-privileged qemu or a stub domain. (Patch 1, combining the fix to both these two issues.) In addition handling of XENMEM_decrease_reservation can also trigger a host crash when the specified page order is neither 4k nor 2M nor 1G (CVE-2021-28708, patch 2).
Credit: security@xen.org security@xen.org
| Affected Software | Affected Version | How to fix |
|---|---|---|
| debian/xen | <=4.11.4+107-gef32c7afa2-1 | 4.14.6-1 4.14.5+94-ge49571868d-1 4.17.1+2-gb773c48e36-1 4.17.2+55-g0b56bed864-1 |
| Xen xen-unstable | >=4.7.0<=4.15.1 | |
| Debian | =11.0 | |
| Fedora | =34 | |
| Fedora | =35 |
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Reference Links
- https://xenbits.xen.org/xsa/advisory-388.html
- https://security-tracker.debian.org/tracker/CVE-2021-28707
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/I7ZGWVVRI4XY2XSTBI3XEMWBXPDVX6OT/
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/PXUI4VMD52CH3T7YXAG3J2JW7ZNN3SXF/
- https://www.debian.org/security/2021/dsa-5017
- https://xenbits.xenproject.org/xsa/advisory-388.txt
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/I7ZGWVVRI4XY2XSTBI3XEMWBXPDVX6OT/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/PXUI4VMD52CH3T7YXAG3J2JW7ZNN3SXF/
- https://security.gentoo.org/glsa/202402-07
Frequently Asked Questions
What is the severity of CVE-2021-28707?
CVE-2021-28707 is considered a moderate severity vulnerability.
How do I fix CVE-2021-28707?
To fix CVE-2021-28707, update to the latest version of affected packages such as Xen and ensure your system is running an updated kernel.
What types of systems are affected by CVE-2021-28707?
CVE-2021-28707 affects x86 HVM and PVH guests that are started in populate-on-demand (PoD) mode.
Can CVE-2021-28707 lead to any security risks?
Yes, CVE-2021-28707 could potentially expose systems to memory-related issues.
What is the impact of exploitation of CVE-2021-28707?
Exploitation of CVE-2021-28707 may allow unauthorized access to memory resources within the affected virtual environments.
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