Linux Distros Unpatched Vulnerability : CVE-2020-15567

high Nessus Plugin ID 257748

Synopsis

The Linux/Unix host has one or more packages installed with a vulnerability that the vendor indicates will not be patched.

Description

The Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied patch available.

- An issue was discovered in Xen through 4.13.x, allowing Intel guest OS users to gain privileges or cause a denial of service because of non-atomic modification of a live EPT PTE. When mapping guest EPT (nested paging) tables, Xen would in some circumstances use a series of non-atomic bitfield writes. Depending on the compiler version and optimisation flags, Xen might expose a dangerous partially written PTE to the hardware, which an attacker might be able to race to exploit. A guest administrator or perhaps even an unprivileged guest user might be able to cause denial of service, data corruption, or privilege escalation. Only systems using Intel CPUs are vulnerable. Systems using AMD CPUs, and Arm systems, are not vulnerable. Only systems using nested paging (hap, aka nested paging, aka in this case Intel EPT) are vulnerable. Only HVM and PVH guests can exploit the vulnerability. The presence and scope of the vulnerability depends on the precise optimisations performed by the compiler used to build Xen. If the compiler generates (a) a single 64-bit write, or (b) a series of read-modify-write operations in the same order as the source code, the hypervisor is not vulnerable. For example, in one test build using GCC 8.3 with normal settings, the compiler generated multiple (unlocked) read-modify-write operations in source- code order, which did not constitute a vulnerability. We have not been able to survey compilers;
consequently we cannot say which compiler(s) might produce vulnerable code (with which code-generation options). The source code clearly violates the C rules, and thus should be considered vulnerable.
(CVE-2020-15567)

Note that Nessus relies on the presence of the package as reported by the vendor.

Solution

There is no known solution at this time.

Plugin Details

Severity: High

ID: 257748

File Name: unpatched_CVE_2020_15567.nasl

Version: 1.1

Type: local

Agent: unix

Family: Misc.

Published: 8/27/2025

Updated: 8/27/2025

Supported Sensors: Agentless Assessment, Frictionless Assessment Agent, Frictionless Assessment AWS, Frictionless Assessment Azure, Nessus Agent, Nessus

Risk Information

VPR

Risk Factor: High

Score: 7.3

CVSS v2

Risk Factor: Medium

Base Score: 4.4

Temporal Score: 3.3

Vector: CVSS2#AV:L/AC:M/Au:N/C:P/I:P/A:P

CVSS Score Source: CVE-2020-15567

CVSS v3

Risk Factor: High

Base Score: 7.8

Temporal Score: 6.8

Vector: CVSS:3.0/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H

Temporal Vector: CVSS:3.0/E:U/RL:O/RC:C

Vulnerability Information

CPE: p-cpe:/a:canonical:ubuntu_linux:xen, cpe:/o:canonical:ubuntu_linux:16.04:-:lts, cpe:/o:canonical:ubuntu_linux:18.04:-:lts

Required KB Items: Host/cpu, Host/local_checks_enabled, global_settings/vendor_unpatched, Host/OS/identifier

Exploit Ease: No known exploits are available

Vulnerability Publication Date: 7/7/2020

Reference Information

CVE: CVE-2020-15567

Detections

Analytics