Buffer overflow in Xen - CVE-2020-11739

Vulnerability identifier: #VU31973

CSH Severity: Medium

CVSS v4: 8.2 [CVSS:4.0/AV:A/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H]

CVE-ID: CVE-2020-11739

CWE-ID: CWE-119

Exploitation vector: Adjecent network

Exploit availability: No public exploit available

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

An issue was discovered in Xen through 4.13.x, allowing guest OS users to cause a denial of service or possibly gain privileges because of missing memory barriers in read-write unlock paths. The read-write unlock paths don't contain a memory barrier. On Arm, this means a processor is allowed to re-order the memory access with the preceding ones. In other words, the unlock may be seen by another processor before all the memory accesses within the "critical" section. As a consequence, it may be possible to have a writer executing a critical section at the same time as readers or another writer. In other words, many of the assumptions (e.g., a variable cannot be modified after a check) in the critical sections are not safe anymore. The read-write locks are used in hypercalls (such as grant-table ones), so a malicious guest could exploit the race. For instance, there is a small window where Xen can leak memory if XENMAPSPACE_grant_table is used concurrently. A malicious guest may be able to leak memory, or cause a hypervisor crash resulting in a Denial of Service (DoS).

Xen
Gentoo Linux
Debian Linux
Opensuse
Ubuntu
Fedora
xen (Alpine package)
xen
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)
libxenevtchn1 (Ubuntu package)
xen (Debian package)

Install updates from vendor's website.

xen (Alpine package) - update to 4.10.4-r3
xen - addressed in versions 4.11.3-4.fc30, 4.11.4-1.fc30, 4.12.2-3.fc31, 4.13.0-7.fc32
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
libxenevtchn1 (Ubuntu package) - update to 4.11.3+24-g14b62ab3e5-1ubuntu2.3
xen (Debian package) - update to 4.11.4+24-gddaaccbbab-1~deb10u1

• http://lists.opensuse.org/opensuse-security-announce/2020-05/msg00006.html
• http://www.openwall.com/lists/oss-security/2020/04/14/2
• http://xenbits.xen.org/xsa/advisory-314.html
• https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/5M2XRNCHOGGTJQBZQJ7DCV6ZNAKN3LE2/
• https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/NVTP4OYHCTRU3ONFJOFJQVNDFB25KLLG/
• https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/YMAW7D2MP6RE4BFI5BZWOBBWGY3VSOFN/
• https://security.gentoo.org/glsa/202005-08
• https://www.debian.org/security/2020/dsa-4723
• https://xenbits.xen.org/xsa/advisory-314.html

• Multiple vulnerabilities in Xen
• OpenSUSE Linux update for xen
• Buffer overflow in xen (Alpine package)
• Gentoo update for Xen
• Debian update for xen
• Ubuntu update for xen
• Fedora 32 update for xen
• Fedora 31 update for xen
• Fedora 30 update for xen
• Fedora 30 update for xen