CVE-2020-29479: 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 th...

Description

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.

Metrics

CVSS 3.1

8.8/10

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H

EPSS Probability

0.30%

22.0th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-862

Affected Software

Vendor	Product	Versions
Xen	Xen	<= 4.14.0
Debian	Debian Linux	10.0
Fedoraproject	Fedora	32
Fedoraproject	Fedora	33

References

Timeline

Published: Dec 15, 2020
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2020-29479?

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.

How severe is CVE-2020-29479?

CVE-2020-29479 has a CVSS score of 8.8/10 (HIGH severity). The EPSS model estimates a 0.30% probability of exploitation in the next 30 days.

How do I fix CVE-2020-29479?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.