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NULL Pointer Dereference Affecting xen package, versions <4.14.1-r0

0.0
medium

Snyk CVSS

    Attack Complexity Low
    Privileges Required High
    Scope Changed
    Availability High

    Threat Intelligence

    EPSS 0.04% (6th percentile)
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NVD
6 medium
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SUSE
6.5 medium

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  • Snyk ID SNYK-ALPINE314-XEN-1308540
  • published 1 Jan 2021
  • disclosed 15 Dec 2020
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Introduced: 15 Dec 2020

CVE-2020-29484 Open this link in a new tab
CWE-476 Open this link in a new tab

How to fix?

Upgrade Alpine:3.14 xen to version 4.14.1-r0 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:3.14 relevant fixed versions and status.

An issue was discovered in Xen through 4.14.x. When a Xenstore watch fires, the xenstore client that registered the watch will receive a Xenstore message containing the path of the modified Xenstore entry that triggered the watch, and the tag that was specified when registering the watch. Any communication with xenstored is done via Xenstore messages, consisting of a message header and the payload. The payload length is limited to 4096 bytes. Any request to xenstored resulting in a response with a payload longer than 4096 bytes will result in an error. When registering a watch, the payload length limit applies to the combined length of the watched path and the specified tag. Because watches for a specific path are also triggered for all nodes below that path, the payload of a watch event message can be longer than the payload needed to register the watch. A malicious guest that registers a watch using a very large tag (i.e., with a registration operation payload length close to the 4096 byte limit) can cause the generation of watch events with a payload length larger than 4096 bytes, by writing to Xenstore entries below the watched path. This will result in an error condition in xenstored. This error can result in a NULL pointer dereference, leading to a crash of xenstored. A malicious guest administrator can cause xenstored to crash, leading to a denial of service. Following a xenstored crash, domains may continue to run, but management operations will be impossible. Only C xenstored is affected, oxenstored is not affected.