Incorrect permission assignment for critical resource in Xen

1) Incorrect permission assignment for critical resource

EUVDB-ID: #VU49129

Risk: Low

CVSSv3.1: 7.7 [CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H/E:U/RL:O/RC:C]

CVE-ID: CVE-2020-29479

CWE-ID: CWE-732 - Incorrect Permission Assignment for Critical Resource

Exploit availability: No

Description

The vulnerability allows a local authenticated user to execute arbitrary code.

An issue was discovered in Xen through 4.14.x. In the Ocaml xenstored implementation, the internal representation of the tree has special cases for the root node, because this node has no parent. Unfortunately, permissions were not checked for certain operations on the root node. Unprivileged guests can get and modify permissions, list, and delete the root node. (Deleting the whole xenstore tree is a host-wide denial of service.) Achieving xenstore write access is also possible. All systems using oxenstored are vulnerable. Building and using oxenstored is the default in the upstream Xen distribution, if the Ocaml compiler is available. Systems using C xenstored are not vulnerable.

Mitigation

Install update from vendor's website.

Vulnerable software versions

Xen: 4.0.0 - 4.14.1

External links

http://www.debian.org/security/2020/dsa-4812
http://xenbits.xenproject.org/xsa/advisory-353.html

Q & A

Can this vulnerability be exploited remotely?

No. This vulnerability can be exploited locally. The attacker should have authentication credentials and successfully authenticate on the system.

Is there known malware, which exploits this vulnerability?

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