PT-2022-2848 · Linux+1 · Linux Kernel+1

Guilherme De Almeida Suckevicz · Published 2022-01-07 · Updated 2026-05-26 · CVE-2021-4095

Positive Technologies (AI Summary)

CVSS v3.1

5.5

Medium

Base vector

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

Name of the Vulnerable Software and Affected Versions Linux kernel versions prior to 5.17-rc1

Description A NULL pointer dereference was found in the Linux kernel's KVM when dirty ring logging is enabled without an active vCPU context. An unprivileged local attacker on the host may use this flaw to cause a kernel oops condition and thus a denial of service by issuing a KVM XEN HVM SET ATTR ioctl.

Recommendations For Linux kernel versions prior to 5.17-rc1, update to version 5.17-rc1 or later to resolve the issue. As a temporary workaround, consider disabling dirty ring logging when no active vCPU context is present to minimize the risk of exploitation. Restrict access to the KVM XEN HVM SET ATTR ioctl to prevent unprivileged local attackers from causing a denial of service.

Exploit

Fix

DoS

NULL Pointer Dereference

Weakness Enumeration

CWE-476

Related Identifiers

ALT-PU-2022-1175

ALT-PU-2022-1647

ALT-PU-2022-2155

ALT-PU-2023-1684

ALT-PU-2023-1741

ALT-PU-2023-1814

ALT-PU-2023-4894

AZL-8965

BDU:2022-03404

CVE-2021-4095

Affected Products

Alt Linux

Linux Kernel

References · 28

• 🔥 https://bugzilla.redhat.com/show_bug.cgi?id=2031194 · Exploit
• 🔥 http://openwall.com/lists/oss-security/2022/01/17/1 · Exploit
• https://linux.oracle.com/errata/ELSA-2022-9534.html · Vendor Advisory
• https://ubuntu.com/security/CVE-2021-4095 · Vendor Advisory
• https://linux.oracle.com/errata/ELSA-2022-9533.html · Vendor Advisory
• https://lists.fedoraproject.org/archives/list/[e-mail]/message/VT6573CGKVK3DU2632VVO5BVM4IU7SBV · Vendor Advisory
• https://bdu.fstec.ru/vul/2022-03404 · Security Note
• https://nvd.nist.gov/vuln/detail/CVE-2021-4095 · Security Note
• https://osv.dev/vulnerability/AZL-8965 · Vendor Advisory
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/VT6573CGKVK3DU2632VVO5BVM4IU7SBV · Vendor Advisory
• https://security-tracker.debian.org/tracker/CVE-2021-4095 · Vendor Advisory
• https://osv.dev/vulnerability/ROOT-OS-UBUNTU-2204-CVE-2021-4095 · Vendor Advisory
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/QIOQN7JJNN6ABIDGRSTVZA65MHRLMH2Q · Vendor Advisory
• https://osv.dev/vulnerability/UBUNTU-CVE-2021-4095 · Vendor Advisory
• https://cve.org/CVERecord?id=CVE-2021-4095 · Security Note