Resource exhaustion in Xen - CVE-2020-25601

Vulnerability identifier: #VU46984

CSH Severity: Medium

CVSS v4: 8.3 [CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H]

CVE-ID: CVE-2020-25601

CWE-ID: CWE-400

Exploitation vector: Remote access

Exploit availability: No public exploit available

The vulnerability allows a remote user to perform a denial of service (DoS) attack.

The vulnerability exists due to improper management of internal resources within the application, as the FIFO event channel model allows guests to have a large number of event channels active at a time.  Closing all of these when resetting all event channels or when cleaning up after the guest may take extended periods of time.  So far there was no arrangement for preemption at suitable intervals, allowing a CPU to spend an almost unbounded amount of time in the processing of these operations. A remote user can consume all available CPU resources and perform a denial of service (DoS) attack of the entire host system.

Xen
Gentoo Linux
Opensuse
Ubuntu
Fedora
xen (Alpine package)
xen (Debian package)
libxenevtchn1 (Ubuntu package)
libxengnttab1 (Ubuntu package)
xen-hypervisor-4.11-amd64 (Ubuntu package)
xen-hypervisor-4.11-armhf (Ubuntu package)
libxenmisc4.11 (Ubuntu package)
libxendevicemodel1 (Ubuntu package)
xenstore-utils (Ubuntu package)
xen-utils-4.11 (Ubuntu package)
xen-hypervisor-4.11-arm64 (Ubuntu package)
xen-utils-common (Ubuntu package)
xen
app-emulation/xen
app-emulation/xen-tools

Install updates from vendor's website.

xen (Alpine package) - update to 4.14.0-r1
xen (Debian package) - update to 4.11.4+37-g3263f257ca-1
libxenevtchn1 (Ubuntu package) - update to 4.11.3+24-g14b62ab3e5-1ubuntu2.3
libxengnttab1 (Ubuntu package) - update to 4.11.3+24-g14b62ab3e5-1ubuntu2.3
xen-hypervisor-4.11-amd64 (Ubuntu package) - update to 4.11.3+24-g14b62ab3e5-1ubuntu2.3
xen-hypervisor-4.11-armhf (Ubuntu package) - update to 4.11.3+24-g14b62ab3e5-1ubuntu2.3
libxenmisc4.11 (Ubuntu package) - update to 4.11.3+24-g14b62ab3e5-1ubuntu2.3
libxendevicemodel1 (Ubuntu package) - update to 4.11.3+24-g14b62ab3e5-1ubuntu2.3
xenstore-utils (Ubuntu package) - update to 4.11.3+24-g14b62ab3e5-1ubuntu2.3
xen-utils-4.11 (Ubuntu package) - update to 4.11.3+24-g14b62ab3e5-1ubuntu2.3
xen-hypervisor-4.11-arm64 (Ubuntu package) - update to 4.11.3+24-g14b62ab3e5-1ubuntu2.3
xen-utils-common (Ubuntu package) - update to 4.11.3+24-g14b62ab3e5-1ubuntu2.3
xen - addressed in versions 4.12.3-5.fc31, 4.13.1-6.fc32, 4.14.0-5.fc33
app-emulation/xen - update to 4.13.2
app-emulation/xen-tools - update to 4.13.2

• https://xenbits.xen.org/xsa/advisory-344.html

• Multiple vulnerabilities in Xen
• Resource exhaustion in xen (Alpine package)
• OpenSUSE Linux update for xen
• Debian update for xen
• Ubuntu update for xen
• Gentoo update for Xen
• Fedora 32 update for xen
• Fedora 31 update for xen
• Fedora 33 update for xen