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Fencer Vulns
high 8.8

CVE-2021-34866 json

This vulnerability allows local attackers to escalate privileges on affected installations of Linux Kernel 5.14-rc3.

published 2022-01-25 4 y ago modified 2026-10-08 31 d ago also EUVD-2021-21513

cvss
8.8
version 3.0, CNA
cisa kev
Not listed
not in CISA's catalog
epss
1.0%
EPSS 1.0% chance of exploitation in 30 days, percentile 62%
public exploits
0
none known

Summary

This vulnerability allows local attackers to escalate privileges on affected installations of Linux Kernel 5.14-rc3. An attacker must first obtain the ability to execute low-privileged code on the target system in order to exploit this vulnerability. The specific flaw exists within the handling of eBPF programs. The issue results from the lack of proper validation of user-supplied eBPF programs, which can result in a type confusion condition. An attacker can leverage this vulnerability to escalate privileges and execute arbitrary code in the context of the kernel. Was ZDI-CAN-14689.

Patch / fix

  • linux linux_kernel 5.10.62, 5.13.14
  • linux Debian 14, Debian 13, Debian 12 5.14.6-1

debian advisories DEBIAN-CVE-2021-34866

  • linux-aws-5.11 Ubuntu 20.04 LTS 5.11.0-1020.21~20.04.2
  • linux-gcp-5.11 Ubuntu 20.04 LTS 5.11.0-1021.23~20.04.1
  • linux-hwe-5.11 Ubuntu 20.04 LTS 5.11.0-38.42~20.04.1
  • linux-oem-5.10 Ubuntu 20.04 LTS 5.10.0-1050.52
  • linux-oem-5.13 Ubuntu 20.04 LTS 5.13.0-1017.21
  • linux-azure-5.11 Ubuntu 20.04 LTS 5.11.0-1020.21~20.04.1
  • linux-riscv-5.11 Ubuntu 20.04 LTS 5.11.0-1021.22~20.04.1
  • linux-oracle-5.11 Ubuntu 20.04 LTS 5.11.0-1020.21~20.04.1

ubuntu advisories UBUNTU-CVE-2021-34866

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • perf rhev hypervisor 4.4, RHEL 8.6 EUS 4.18.0-372.91.1.el8_6
  • kernel RHEL 8.6 EUS 4.18.0-372.91.1.el8_6
  • bpftool RHEL 8.6 EUS 4.18.0-372.91.1.el8_6
  • kernel-core RHEL 8.6 EUS 4.18.0-372.91.1.el8_6
  • kernel-tools RHEL 8.6 EUS 4.18.0-372.91.1.el8_6
  • python3-perf RHEL 8.6 EUS 4.18.0-372.91.1.el8_6
  • kernel-modules RHEL 8.6 EUS 4.18.0-372.91.1.el8_6
  • kernel-zfcpdump RHEL 8.6 EUS 4.18.0-372.91.1.el8_6

red hat advisories RHSA-2024:0724

  • kernel-64kb SLE Module for Basesystem 15 SP3 5.3.18-59.34.1
  • kernel-syms SLE Module for Development Tools 15 SP3 5.3.18-59.34.1
  • kernel-source SLE Module for Development Tools 15 SP3, SLE Module for Basesystem 15 SP3 5.3.18-59.34.1
  • kernel-default SLE Workstation Extension 15 SP3, SLE Module for Legacy 15 SP3, SLE Module for Basesystem 15 SP3 +3 more 5.3.18-59.34.1
  • kernel-preempt SLE Workstation Extension 15 SP3, SLE Module for Development Tools 15 SP3, SLE Module for Basesystem 15 SP3 5.3.18-59.34.1
  • kernel-zfcpdump SLE Module for Basesystem 15 SP3 5.3.18-59.34.1
  • kernel-obs-build SLE Module for Development Tools 15 SP3 5.3.18-59.34.1
  • kernel-default-base SLE Module for Basesystem 15 SP3, SLE Micro 5.1 5.3.18-59.34.1.18.21.1

suse advisories SUSE-SU-2021:3742-1SUSE-SU-2021:3738-1SUSE-SU-2021:3718-1SUSE-SU-2021:3675-1SUSE-SU-2021:3642-1SUSE-SU-2021:3641-1

  • dtb-aarch64 openSUSE Leap 15.3 5.3.18-59.34.1
  • kernel-64kb openSUSE Leap 15.3 5.3.18-59.34.1
  • kernel-syms openSUSE Leap 15.3 5.3.18-59.34.1
  • kernel-obs-qa openSUSE Leap 15.3 5.3.18-59.34.1
  • kernel-source openSUSE Leap 15.3 5.3.18-59.34.1
  • kernel-default openSUSE Leap 15.3 5.3.18-59.34.1
  • kernel-preempt openSUSE Leap 15.3 5.3.18-59.34.1
  • kernel-kvmsmall openSUSE Leap 15.3 5.3.18-59.34.1

opensuse advisories openSUSE-SU-2021:3675-1openSUSE-SU-2021:3641-1

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2021-34866 updated cvss 6.7

kernel: eBPF verification flaw

  • Red Hat Enterprise Linux 7 perf, kernel, bpftool, kernel-rt, python-perf, kernel-kdump, +8 more
    affected: workaround, no fix planned “Out of support scope”
  • Red Hat Enterprise Linux 8 perf, kernel, bpftool, kernel-rt, kernel-core, kernel-tools, +29 more
    affected: workaround, no fix available
  • Red Hat Enterprise Linux 9 rv, perf, rtla, kernel, bpftool, libperf, +82 more
    affected: workaround, no fix planned “Will not fix”
  • Red Hat CodeReady Linux Builder EUS (v.8.6) kernel-debuginfo-common-x86_64 4.18.0-372.91.1.el8_6, kernel-debuginfo-common-aarch64 4.18.0-372.91.1.el8_6, kernel-debuginfo-common-ppc64le 4.18.0-372.91.1.el8_6 Red Hat Enterprise Linux BaseOS EUS (v.8.6) perf 4.18.0-372.91.1.el8_6, kernel 4.18.0-372.91.1.el8_6, bpftool 4.18.0-372.91.1.el8_6, kernel-core 4.18.0-372.91.1.el8_6, kernel-tools 4.18.0-372.91.1.el8_6, python3-perf 4.18.0-372.91.1.el8_6, +15 more Red Hat Virtualization 4 Hypervisor for RHEL 8 perf 4.18.0-372.91.1.el8_6, kernel-debuginfo-common-x86_64 4.18.0-372.91.1.el8_6
    fixed: vendor fix RHSA-2024:0724
  • Red Hat Enterprise Linux 5 kernel Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 more
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
total
Assessed
31 d ago

Exploit prediction

0.97% chance of exploitation in the next 30 days, higher than 62% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.0 8.8 CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
NVD 3.1 7.8 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
NVD 2.0 7.2 AV:L/AC:L/Au:N/C:C/I:C/A:C

Affected products

  • Linux Kernel

Classification

Weakness
  • CWE-843 Access of Resource Using Incompatible Type
Technology feeds

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.