NULL pointer dereference in Xen

1) NULL pointer dereference

EUVDB-ID: #VU49140

Risk: Medium

CVSSv3.1: 5.7 [CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H/E:U/RL:O/RC:C]

CVE-ID: CVE-2020-29571

CWE-ID: CWE-476 - NULL Pointer Dereference

Exploit availability: No

Description

The vulnerability allows a remote non-authenticated attacker to perform a denial of service (DoS) attack.

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.

Mitigation

Install update from vendor's website.

Vulnerable software versions

Xen: 4.0.0 - 4.14.1

CPE2.3

• cpe:2.3:a:xen_project:xen:4.0.0:*:*:*:*:*:*:*
• cpe:2.3:a:xen_project:xen:4.0.1:*:*:*:*:*:*:*
• cpe:2.3:a:xen_project:xen:4.0.2:*:*:*:*:*:*:*

External links

http://www.debian.org/security/2020/dsa-4812
http://xenbits.xenproject.org/xsa/advisory-359.html

Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the Internet.

Is there known malware, which exploits this vulnerability?

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