CVE-2020-25604

Name	CVE-2020-25604
Description	An issue was discovered in Xen through 4.14.x. There is a race condition when migrating timers between x86 HVM vCPUs. When migrating timers of x86 HVM guests between its vCPUs, the locking model used allows for a second vCPU of the same guest (also operating on the timers) to release a lock that it didn't acquire. The most likely effect of the issue is a hang or crash of the hypervisor, i.e., a Denial of Service (DoS). All versions of Xen are affected. Only x86 systems are vulnerable. Arm systems are not vulnerable. Only x86 HVM guests can leverage the vulnerability. x86 PV and PVH cannot leverage the vulnerability. Only guests with more than one vCPU can exploit the vulnerability.
Source	CVE (at NVD; CERT, LWN, oss-sec, fulldisc, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more)
References	DSA-4769-1

Vulnerable and fixed packages

The table below lists information on source packages.

Source Package	Release	Version	Status
xen (PTS)	jessie, jessie (lts)	4.4.4lts5-0+deb8u1	vulnerable
	stretch (security), stretch (lts), stretch	4.8.5.final+shim4.10.4-1+deb9u12	vulnerable
	buster, buster (security)	4.11.4+107-gef32c7afa2-1	fixed
	bullseye	4.14.6-1	fixed
	bullseye (security)	4.14.5+94-ge49571868d-1	fixed
	bookworm	4.17.3+10-g091466ba55-1~deb12u1	fixed
	trixie	4.17.3+10-g091466ba55-1	fixed
	sid	4.17.3+36-g54dacb5c02-1	fixed

The information below is based on the following data on fixed versions.

Package	Type	Release	Fixed Version	Urgency	Origin
xen	source	jessie	(unfixed)	end-of-life
xen	source	stretch	(unfixed)	end-of-life
xen	source	buster	4.11.4+37-g3263f257ca-1		DSA-4769-1
xen	source	(unstable)	4.14.0+80-gd101b417b7-1

[stretch] - xen <end-of-life> (DSA 4602-1)
https://xenbits.xen.org/xsa/advisory-336.html