# CVE-2021-4095: linux: A NULL pointer dereference was found in the Linux kernel's KVM when dirty ring logging is enabled without an active v...

CVE-2021-4095 is fixed in 15 products on 1 platform, first by DEBIAN-CVE-2021-4095, released March 10, 2022. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2021-4095
- Priority: Routine
- CVSS: 5.5 (medium)
- EPSS: 0.0039
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Mar 10, 2022

## 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. This flaw affects Linux kernel versions prior to 5.17-rc1.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | bpftool ol 8 | 0:5.15.0-0.30.19.el8uek | [ELSA-2022-9533](https://patchblox.com/security/data/fix/linux/elsa-2022-9533.md) | Jun 30, 2022 |
| Linux | kernel-uek ol 8 | 0:5.15.0-0.30.19.el8uek | [ELSA-2022-9533](https://patchblox.com/security/data/fix/linux/elsa-2022-9533.md) | Jun 30, 2022 |
| Linux | kernel-uek-container ol 8 | 0:5.15.0-0.30.19.el8 | [ELSA-2022-9534](https://patchblox.com/security/data/fix/linux/elsa-2022-9534.md) | Jun 30, 2022 |
| Linux | kernel-uek-container-debug ol 8 | 0:5.15.0-0.30.19.el8 | [ELSA-2022-9534](https://patchblox.com/security/data/fix/linux/elsa-2022-9534.md) | Jun 30, 2022 |
| Linux | kernel-uek-core ol 8 | 0:5.15.0-0.30.19.el8uek | [ELSA-2022-9533](https://patchblox.com/security/data/fix/linux/elsa-2022-9533.md) | Jun 30, 2022 |
| Linux | kernel-uek-debug ol 8 | 0:5.15.0-0.30.19.el8uek | [ELSA-2022-9533](https://patchblox.com/security/data/fix/linux/elsa-2022-9533.md) | Jun 30, 2022 |
| Linux | kernel-uek-debug-core ol 8 | 0:5.15.0-0.30.19.el8uek | [ELSA-2022-9533](https://patchblox.com/security/data/fix/linux/elsa-2022-9533.md) | Jun 30, 2022 |
| Linux | kernel-uek-debug-devel ol 8 | 0:5.15.0-0.30.19.el8uek | [ELSA-2022-9533](https://patchblox.com/security/data/fix/linux/elsa-2022-9533.md) | Jun 30, 2022 |
| Linux | kernel-uek-debug-modules ol 8 | 0:5.15.0-0.30.19.el8uek | [ELSA-2022-9533](https://patchblox.com/security/data/fix/linux/elsa-2022-9533.md) | Jun 30, 2022 |
| Linux | kernel-uek-debug-modules-extra ol 8 | 0:5.15.0-0.30.19.el8uek | [ELSA-2022-9533](https://patchblox.com/security/data/fix/linux/elsa-2022-9533.md) | Jun 30, 2022 |
| Linux | kernel-uek-devel ol 8 | 0:5.15.0-0.30.19.el8uek | [ELSA-2022-9533](https://patchblox.com/security/data/fix/linux/elsa-2022-9533.md) | Jun 30, 2022 |
| Linux | kernel-uek-doc ol 8 | 0:5.15.0-0.30.19.el8uek | [ELSA-2022-9533](https://patchblox.com/security/data/fix/linux/elsa-2022-9533.md) | Jun 30, 2022 |
| Linux | kernel-uek-modules ol 8 | 0:5.15.0-0.30.19.el8uek | [ELSA-2022-9533](https://patchblox.com/security/data/fix/linux/elsa-2022-9533.md) | Jun 30, 2022 |
| Linux | kernel-uek-modules-extra ol 8 | 0:5.15.0-0.30.19.el8uek | [ELSA-2022-9533](https://patchblox.com/security/data/fix/linux/elsa-2022-9533.md) | Jun 30, 2022 |
| Linux | linux Debian 12.15 (bookworm) | 5.17.3-1 | [DEBIAN-CVE-2021-4095](https://patchblox.com/security/data/fix/linux/debian-cve-2021-4095.md) | Mar 10, 2022 |
| Linux | linux Debian 13.5 (trixie) | 5.17.3-1 | [DEBIAN-CVE-2021-4095](https://patchblox.com/security/data/fix/linux/debian-cve-2021-4095.md) | Mar 10, 2022 |
| Linux | linux Debian 14 | 5.17.3-1 | [DEBIAN-CVE-2021-4095](https://patchblox.com/security/data/fix/linux/debian-cve-2021-4095.md) | Mar 10, 2022 |

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