Vulnerability · Published Jul 7, 2020 · Assigned by mitre
CVE-2020-15565
High 8.8
In plain English
A high-severity security flaw in the xen package (Alpine). There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 30% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
An issue was discovered in Xen through 4.13.x, allowing x86 Intel HVM guest OS users to cause a host OS denial of service or possibly gain privileges because of insufficient cache write-back under VT-d. When page tables are shared between IOMMU and CPU, changes to them require flushing of both TLBs. Furthermore, IOMMUs may be non-coherent, and hence prior to flushing IOMMU TLBs, a CPU cache also needs writing back to memory after changes were made. Such writing back of cached data was missing in particular when splitting large page mappings into smaller granularity ones. A malicious guest may be able to retain read/write DMA access to frames returned to Xen's free pool, and later reused for another purpose. Host crashes (leading to a Denial of Service) and privilege escalation cannot be ruled out. Xen versions from at least 3.2 onwards are affected. Only x86 Intel systems are affected. x86 AMD as well as Arm systems are not affected. Only x86 HVM guests using hardware assisted paging (HAP), having a passed through PCI device assigned, and having page table sharing enabled can leverage the vulnerability. Note that page table sharing will be enabled (by default) only if Xen considers IOMMU and CPU large page size support compatible.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine:v3.20 | xen | 4.13.1-r4 | ALPINE-CVE-2020-15565 |
| Alpine:v3.21 | xen | 4.13.1-r4 | ALPINE-CVE-2020-15565 |
| Alpine:v3.22 | xen | 4.13.1-r4 | ALPINE-CVE-2020-15565 |
| Alpine:v3.23 | xen | 4.13.1-r4 | ALPINE-CVE-2020-15565 |
| Alpine:v3.24 | xen | 4.13.1-r4 | ALPINE-CVE-2020-15565 |
| Debian:12 | xen | 4.11.4+24-gddaaccbbab-1 | DEBIAN-CVE-2020-15565 |
| Debian:13 | xen | 4.11.4+24-gddaaccbbab-1 | DEBIAN-CVE-2020-15565 |
| Debian:14 | xen | 4.11.4+24-gddaaccbbab-1 | DEBIAN-CVE-2020-15565 |
Affected products (as reported)
References
- http://xenbits.xen.org/xsa/advisory-321.html x_refsource_MISC
- [oss-security] 20200707 Xen Security Advisory 321 v3 (CVE-2020-15565) - insufficient cache write-back under VT-d mailing-list, x_refsource_MLIST
- DSA-4723 vendor-advisory, x_refsource_DEBIAN
- openSUSE-SU-2020:0965 vendor-advisory, x_refsource_SUSE
- FEDORA-2020-fbc13516af vendor-advisory, x_refsource_FEDORA
- openSUSE-SU-2020:0985 vendor-advisory, x_refsource_SUSE
- FEDORA-2020-76cf2b0f0a vendor-advisory, x_refsource_FEDORA
- GLSA-202007-02 vendor-advisory, x_refsource_GENTOO