What is CVE-2021-20239?

CVE-2021-20239 is a low-severity vulnerability in Linux Kernel, classified under Untrusted Pointer Dereference. CVSS score: 3.3/10. Published 2021-05-28.

How severe is CVE-2021-20239?

Low severity. CVSS v3 base score is 3.3 out of 10.

Buffer overflow in Linux Kernel

CVE-2021-20239

A flaw was found in the Linux kernel in versions before 5.4.92 in the BPF protocol. This flaw allows an attacker with a local account to leak information about kernel internal addresses. The highest threat from this vulnerability is to confidentiality.

Published 2021-05-28 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 3.3 (Low). Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N.

EPSS exploit prediction

EPSS: 0.003 (15.5th percentile), scored 2026-10-02.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 16th percentile — 15.5% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.003 · newest: 0.003 · change: 0.000

Affected products

Linux Kernel
Fedoraproject Fedora — versions 33
Red Hat Enterprise Linux — versions 5.0, 6.0, 8.0
Kernel — versions kernel 5.4.92

Weakness classification (CWE)

References

bugzilla.redhat.com/show_bug.cgi (Third Party Advisory, Issue Tracking)

Frequently asked questions

What is CVE-2021-20239?: CVE-2021-20239 is a low-severity vulnerability in Linux Kernel, classified under Untrusted Pointer Dereference. CVSS score: 3.3/10. Published 2021-05-28.
How severe is CVE-2021-20239?: Low severity. CVSS v3 base score is 3.3 out of 10.