Skip to content
Fencer Intel
medium 4.4

CVE-2021-4159 json

A vulnerability was found in the Linux kernel's EBPF verifier when handling internal data structures.

published 4y ago modified 7d ago also EUVD-2021-34027

cvss
4.4
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.2%
EPSS 0.2% chance of exploitation in 30 days, percentile 16%
public exploits
0
none known

Summary

A vulnerability was found in the Linux kernel's EBPF verifier when handling internal data structures. Internal memory locations could be returned to userspace. A local attacker with the permissions to insert eBPF code to the kernel can use this to leak internal kernel memory details defeating some of the exploit mitigations in place for the kernel.

Patch / fix

  • linux linux_kernel 5.7
  • linux Debian 14, Debian 13, Debian 12 5.7.6-1

debian advisories DEBIAN-CVE-2021-4159

  • linux Ubuntu 18.04 LTS 4.15.0-201.212
  • linux Ubuntu 20.04 LTS 5.4.0-128.144
  • linux-aws Ubuntu 18.04 LTS 4.15.0-1147.159
  • linux-aws Ubuntu 20.04 LTS 5.4.0-1086.93
  • linux-gcp Ubuntu 20.04 LTS 5.4.0-1090.98
  • linux-gke Ubuntu 20.04 LTS 5.4.0-1084.90
  • linux-ibm Ubuntu 20.04 LTS 5.4.0-1034.38
  • linux-iot Ubuntu 20.04 LTS 5.4.0-1005.7

ubuntu advisories UBUNTU-CVE-2021-4159

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

  • kernel-azure SLE Module for Public Cloud 15 SP3 5.3.18-150300.38.40.4
  • kernel-syms-azure SLE Module for Public Cloud 15 SP3 5.3.18-150300.38.40.1
  • kernel-source-azure SLE Module for Public Cloud 15 SP3 5.3.18-150300.38.40.4
  • kernel-syms SLES LTSS Extended Security 12 SP5, SLES 12 SP5-LTSS 4.12.14-122.261.1
  • kernel-source SLES LTSS Extended Security 12 SP5, SLES 12 SP5-LTSS 4.12.14-122.261.1
  • kernel-default SLES LTSS Extended Security 12 SP5, SLES 12 SP5-LTSS, SLE Live Patching 12 SP5 4.12.14-122.261.1
  • kgraft-patch-SLE12-SP5_Update_69 SLE Live Patching 12 SP5 1-8.3.1

suse advisories SUSE-SU-2025:01983-1SUSE-SU-2022:0363-1

  • kernel-azure openSUSE Leap 15.3 5.3.18-150300.38.40.4
  • kernel-syms-azure openSUSE Leap 15.3 5.3.18-150300.38.40.1
  • kernel-source-azure openSUSE Leap 15.3 5.3.18-150300.38.40.4

opensuse advisories openSUSE-SU-2022:0363-1

Is CVE-2021-4159 in your stack? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

Check with Fencer

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-2021-4159 updated cvss 4.4

kernel: another kernel ptr leak vulnerability via BPF in coerce_reg_to_size

  • Red Hat Enterprise Linux 5 kernel Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 more
    affected: workaround, no fix planned “Out of support scope”
  • Red Hat Enterprise Linux 7 perf, kernel, bpftool, kernel-rt, python-perf, kernel-kdump, +8 more
    affected: workaround, no fix planned “Will not fix”
  • Red Hat Enterprise Linux 8 perf, kernel, bpftool, kernel-rt, kernel-core, kernel-tools, +29 more
    affected: workaround, no fix available
  • Red Hat Enterprise MRG 2 kernel
    under investigation
  • Red Hat Enterprise Linux 9 rv, perf, rtla, kernel, bpftool, libperf, +83 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
partial
Assessed
last mo.

Exploit prediction

0.25% chance of exploitation in the next 30 days, higher than 16% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
NVD 3.1 4.4 CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:N/A:N

Affected products

  • n/a kernel

Classification

Weakness
  • CWE-202 Exposure of Sensitive Information Through Data Queries
Technology feeds

References

Sources

Fencer Intel 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.