---
id: CVE-2020-27171
title: An issue was discovered in the Linux kernel before 5.11.8
summary: >-
  An issue was discovered in the Linux kernel before 5.11.8.
  kernel/bpf/verifier.c has an off-by-one error (with a resultant integer
  underflow) affecting out-of-bounds speculation on pointer arithmetic, leading
  to side-channel attacks that…
severity: medium
cvss: 6
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:N/A:H'
cwe:
  - CWE-193
vendor: linux
product: linux_kernel
affected:
  - linux_kernel < 5.11.8
  - fedora = 32
  - fedora = 33
  - fedora = 34
  - debian_linux = 9.0
  - ubuntu_linux = 14.04
  - ubuntu_linux = 16.04
  - ubuntu_linux = 18.04
  - ubuntu_linux = 20.04
patched:
  - linux_kernel 5.11.8
published: '2021-03-20'
updated: '2026-10-08'
sourceUpdated: '2026-10-08T21:17:27.333'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2020-27171'
references:
  - url: >-
      http://packetstormsecurity.com/files/162117/Kernel-Live-Patch-Security-Notice-LSN-0075-1.html
    label: cve@mitre.org
  - url: 'http://www.openwall.com/lists/oss-security/2021/03/24/5'
    label: cve@mitre.org
  - url: 'https://cdn.kernel.org/pub/linux/kernel/v5.x/ChangeLog-5.11.8'
    label: cve@mitre.org
  - url: >-
      https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf.git/patch/?id=10d2bb2e6b1d8c4576c56a748f697dbeb8388899
    label: cve@mitre.org
  - url: 'https://lists.debian.org/debian-lts-announce/2021/03/msg00035.html'
    label: cve@mitre.org
  - url: >-
      https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/FB6LUXPEIRLZH32YXWZVEZAD4ZL6SDK2/
    label: cve@mitre.org
  - url: >-
      https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/QRTPQE73ANG7D6M4L4PK5ZQDPO4Y2FVD/
    label: cve@mitre.org
  - url: >-
      https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/T2S3I4SLRNRUQDOFYUS6IUAZMQNMPNLG/
    label: cve@mitre.org
  - url: 'https://www.openwall.com/lists/oss-security/2021/03/19/3'
    label: cve@mitre.org
  - url: >-
      http://packetstormsecurity.com/files/162117/Kernel-Live-Patch-Security-Notice-LSN-0075-1.html
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'http://www.openwall.com/lists/oss-security/2021/03/24/5'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://cdn.kernel.org/pub/linux/kernel/v5.x/ChangeLog-5.11.8'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: >-
      https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf.git/patch/?id=10d2bb2e6b1d8c4576c56a748f697dbeb8388899
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://lists.debian.org/debian-lts-announce/2021/03/msg00035.html'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: >-
      https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/FB6LUXPEIRLZH32YXWZVEZAD4ZL6SDK2/
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: >-
      https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/QRTPQE73ANG7D6M4L4PK5ZQDPO4Y2FVD/
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: >-
      https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/T2S3I4SLRNRUQDOFYUS6IUAZMQNMPNLG/
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://www.openwall.com/lists/oss-security/2021/03/19/3'
    label: af854a3a-2127-422b-91ae-364da2661108
tags:
  - nvd
  - cve.org
epss: 0.00577
epssPercentile: 0.47356
ingestedAt: '2026-10-08T22:11:53.730Z'
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-10-08T20:57:10.613050Z'
---

## Overview

An issue was discovered in the Linux kernel before 5.11.8. kernel/bpf/verifier.c has an off-by-one error (with a resultant integer underflow) affecting out-of-bounds speculation on pointer arithmetic, leading to side-channel attacks that defeat Spectre mitigations and obtain sensitive information from kernel memory, aka CID-10d2bb2e6b1d.

## Affected

- `linux_kernel < 5.11.8`
- `fedora = 32`
- `fedora = 33`
- `fedora = 34`
- `debian_linux = 9.0`
- `ubuntu_linux = 14.04`
- `ubuntu_linux = 16.04`
- `ubuntu_linux = 18.04`
- `ubuntu_linux = 20.04`

## Remediation

Upgrade past the affected range:

- `linux_kernel 5.11.8`