CVE-2020-29484: 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…

PriorityP419medium6CVSS 3.1

AVLACLPRHUINSCCNINAH

EPSS

0.39%

31.2th percentile

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.

Affected

9 ranges

Vendor	Product	Version range	Fixed in
debian	debian_linux	—	—
debian	xen	< xen 4.14.0+88-g1d1d1f5391-1 (bookworm)	xen 4.14.0+88-g1d1d1f5391-1 (bookworm)
fedoraproject	fedora	—	—
fedoraproject	fedora	—	—
xen	xen	<= 4.14.0	—
xen	xen	>= 0 < 4.14.0+88-g1d1d1f5391-1	4.14.0+88-g1d1d1f5391-1
xen	xen	>= 0 < 4.14.0+88-g1d1d1f5391-1	4.14.0+88-g1d1d1f5391-1
xen	xen	>= 0 < 4.14.0+88-g1d1d1f5391-1	4.14.0+88-g1d1d1f5391-1
xen	xen	>= 0 < 4.14.0+88-g1d1d1f5391-1	4.14.0+88-g1d1d1f5391-1

CVSS provenance

nvdv3.16.0MEDIUMCVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:C/C:N/I:N/A:H

nvdv2.04.9MEDIUMAV:L/AC:L/Au:N/C:N/I:N/A:C

osv6.0MEDIUM

vendor_debian6.0MEDIUM

Stop checking back — get the weekly exploitation signal.

Every Monday: what got weaponized or added to CISA KEV in the last seven days — each CVE cross-linked to its PoC, Nuclei template, and detection rule. Free, one email a week, unsubscribe in one click.