--- title: "CVE-2020-15565\n | Ubuntu" description: Ubuntu is an open source software operating system that runs from the desktop, to the cloud, to all your internet connected things. url: https://ubuntu.com/security/CVE-2020-15565?format=md keywords: index, follow --- # CVE-2020-15565 Publication date 7 July 2020 Last updated 26 August 2025 --- Ubuntu priority **Medium** [Why this priority?](https://ubuntu.com/security/cves/about#priority ) ## Cvss 3 Severity Score **8.8 · High** [Score breakdown](https://ubuntu.com/security/CVE-2020-15565?format=md#impact-score) Toggle side navigation ## 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. [Read the notes from the security team](https://ubuntu.com/security/CVE-2020-15565?format=md#notes) ## Status Show unmaintained releases | Package | Ubuntu Release | Status | | --- | --- | --- | | xen | 26.04 LTS resolute | Not affected | | 25.10 questing | Not affected | | 25.04 plucky | Not affected | | 24.10 oracular | Not affected | | 24.04 LTS noble | Not affected | | 23.10 mantic | Not affected | | 23.04 lunar | Not affected | | 22.10 kinetic | Not affected | | 22.04 LTS jammy | Not affected | | 21.10 impish | Not affected | | 21.04 hirsute | Not affected | | 20.10 groovy | Not affected | | 20.04 LTS focal | Fixed 4.11.3+24-g14b62ab3e5-1ubuntu2.3 | | 19.10 eoan | Ignored end of life | | 18.04 LTS bionic | Vulnerable | | 16.04 LTS xenial | Vulnerable | | 14.04 LTS trusty | Not in release | --- * [How can I get the fixes?](https://ubuntu.com/security/cves/about#security) * [What do statuses mean?](https://ubuntu.com/security/cves/about#statuses) ## Notes --- ### [mdeslaur](https://launchpad.net/~mdeslaur) hypervisor packages are in universe. For issues in the hypervisor, add appropriate tags to each section, ex: Tags\_xen: universe-binary ## Severity score breakdown CVSS version: CVSS v3.0 **Base score** 8.8 · High * Base metrics | Parameter | Value | | --- | --- | | Attack vector | Local | | Attack complexity | Low | | Privileges required | Low | | User interaction | None | | Scope | Changed | | Confidentiality impact | High | | Integrity impact | High | | Availability impact | High | * Scores | Parameter | Value | | --- | --- | | Base score | 8.8 · High | | Exploitability score | - | | Impact score | - | **Vector:** CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H ## References * [MITRE](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2020-15565) * [NVD](https://nvd.nist.gov/vuln/detail/CVE-2020-15565) * [Launchpad](https://launchpad.net/bugs/cve/CVE-2020-15565) * [Debian](https://security-tracker.debian.org/tracker/CVE-2020-15565) ### Related Ubuntu Security Notices (USN) + [USN-5617-1](https://usn.ubuntu.com/USN-5617-1) + Xen vulnerabilities + 19 September 2022 ### Other references * * * *