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Always-Incorrect Control Flow Implementation Affecting xen package, versions <4.14.0-r1

0.0
medium

Snyk CVSS

    Attack Complexity Low
    Availability High

    Threat Intelligence

    EPSS 0.05% (14th percentile)
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NVD
5.5 medium
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SUSE
6.5 medium

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  • Snyk ID SNYK-ALPINE315-XEN-1930023
  • published 24 Sep 2020
  • disclosed 23 Sep 2020
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Introduced: 23 Sep 2020

CVE-2020-25598 Open this link in a new tab
CWE-670 Open this link in a new tab

How to fix?

Upgrade Alpine:3.15 xen to version 4.14.0-r1 or higher.

NVD Description

Note: Versions mentioned in the description apply only to the upstream xen package and not the xen package as distributed by Alpine. See How to fix? for Alpine:3.15 relevant fixed versions and status.

An issue was discovered in Xen 4.14.x. There is a missing unlock in the XENMEM_acquire_resource error path. The RCU (Read, Copy, Update) mechanism is a synchronisation primitive. A buggy error path in the XENMEM_acquire_resource exits without releasing an RCU reference, which is conceptually similar to forgetting to unlock a spinlock. A buggy or malicious HVM stubdomain can cause an RCU reference to be leaked. This causes subsequent administration operations, (e.g., CPU offline) to livelock, resulting in a host Denial of Service. The buggy codepath has been present since Xen 4.12. Xen 4.14 and later are vulnerable to the DoS. The side effects are believed to be benign on Xen 4.12 and 4.13, but patches are provided nevertheless. The vulnerability can generally only be exploited by x86 HVM VMs, as these are generally the only type of VM that have a Qemu stubdomain. x86 PV and PVH domains, as well as ARM VMs, typically don't use a stubdomain. Only VMs using HVM stubdomains can exploit the vulnerability. VMs using PV stubdomains, or with emulators running in dom0, cannot exploit the vulnerability.

References