Vulnerability identifier: #VU31972

Vulnerability risk: Medium

CVSSv3.1: 5.9 [CVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H/E:U/RL:O/RC:C]

CVE-ID: CVE-2020-11743

CWE-ID: CWE-755

Exploitation vector: Local network

Exploit availability: No

Vulnerable software:
Xen
Server applications / Virtualization software

Vendor: Xen Project

Description

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 because of a bad error path in GNTTABOP_map_grant. Grant table operations are expected to return 0 for success, and a negative number for errors. Some misplaced brackets cause one error path to return 1 instead of a negative value. The grant table code in Linux treats this condition as success, and proceeds with incorrectly initialised state. A buggy or malicious guest can construct its grant table in such a way that, when a backend domain tries to map a grant, it hits the incorrect error path. This will crash a Linux based dom0 or backend domain.

Mitigation
Install updates from vendor's website.

Vulnerable software versions

Xen: 4.0.0 - 4.13.0

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External links
http://lists.opensuse.org/opensuse-security-announce/2020-05/msg00006.html
http://www.openwall.com/lists/oss-security/2020/04/14/3
http://xenbits.xen.org/xsa/advisory-316.html
http://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/5M2XRNCHOGGTJQBZQJ7DCV6ZNAKN3LE2/
http://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/NVTP4OYHCTRU3ONFJOFJQVNDFB25KLLG/
http://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/YMAW7D2MP6RE4BFI5BZWOBBWGY3VSOFN/
http://security.gentoo.org/glsa/202005-08
http://www.debian.org/security/2020/dsa-4723
http://xenbits.xen.org/xsa/advisory-316.html

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Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote authenticated user via the local network (LAN).

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.