CVE-2020-29571: An issue was discovered in Xen through 4.14.x. A bounds check common to most operation time functions specific to FIFO event channels depends on the C...

Description

An issue was discovered in Xen through 4.14.x. A bounds check common to most operation time functions specific to FIFO event channels depends on the CPU observing consistent state. While the producer side uses appropriately ordered writes, the consumer side isn't protected against re-ordered reads, and may hence end up de-referencing a NULL pointer. Malicious or buggy guest kernels can mount a Denial of Service (DoS) attack affecting the entire system. Only Arm systems may be vulnerable. Whether a system is vulnerable depends on the specific CPU. x86 systems are not vulnerable.

Metrics

CVSS 3.1

6.2/10

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

EPSS Probability

0.38%

29.8th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-476

Affected Software

Vendor	Product	Versions
Xen	Xen	>= 4.4.0, <= 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-2020-29571?

An issue was discovered in Xen through 4.14.x. A bounds check common to most operation time functions specific to FIFO event channels depends on the CPU observing consistent state. While the producer side uses appropriately ordered writes, the consumer side isn't protected against re-ordered reads, and may hence end up de-referencing a NULL pointer. Malicious or buggy guest kernels can mount a Denial of Service (DoS) attack affecting the entire system. Only Arm systems may be vulnerable. Whether a system is vulnerable depends on the specific CPU. x86 systems are not vulnerable.

How severe is CVE-2020-29571?

CVE-2020-29571 has a CVSS score of 6.2/10 (MEDIUM severity). The EPSS model estimates a 0.38% probability of exploitation in the next 30 days.

How do I fix CVE-2020-29571?

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.