What is CVE-2021-3564?

CVE-2021-3564 is a medium-severity vulnerability in Linux Kernel, classified under Double Free. CVSS score: 5.5/10. Published 2021-06-08.

How severe is CVE-2021-3564?

Medium severity. CVSS v3 base score is 5.5 out of 10.

Is CVE-2021-3564 known to be exploited?

1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.

Double Free in Linux Kernel

CVE-2021-3564

A flaw double-free memory corruption in the Linux kernel HCI device initialization subsystem was found in the way user attach malicious HCI TTY Bluetooth device. A local user could use this flaw to crash the system. This flaw affects all the Linux kernel versions starting from 3.13.

Vulnerability class: Double Free

Published 2021-06-08 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 5.5 (Medium). Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H.

EPSS exploit prediction

EPSS: 0.005 (39.4th percentile), scored 2026-10-01.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 39th percentile — 39.4% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.005 · newest: 0.005 · change: 0.000

Affected products

Linux Kernel
Debian Linux — versions 9.0
Fedoraproject Fedora — versions 34
Kernel — versions All Linux kernel versions starting from 3.13

Weakness classification (CWE)

CWE-415 — Double Free

Public proof-of-concept exploits

ARPSyndicate/cvemon

References

www.openwall.com/lists/oss-security/2021/05/25/1 (mailing-list, Exploit, Mailing List, Third Party Advisory)
www.openwall.com/lists/oss-security/2021/06/01/2 (mailing-list, Exploit, Mailing List)
bugzilla.redhat.com/show_bug.cgi (Third Party Advisory, Issue Tracking)
www.openwall.com/lists/oss-security/2021/05/25/1 (Exploit, Mailing List, Third Party Advisory)
lists.debian.org/debian-lts-announce/2021/06/msg00020.html (mailing-list, Third Party Advisory)
lists.debian.org/debian-lts-announce/2021/06/msg00019.html (mailing-list, Third Party Advisory)

Frequently asked questions

What is CVE-2021-3564?: CVE-2021-3564 is a medium-severity vulnerability in Linux Kernel, classified under Double Free. CVSS score: 5.5/10. Published 2021-06-08.
How severe is CVE-2021-3564?: Medium severity. CVSS v3 base score is 5.5 out of 10.
Is CVE-2021-3564 known to be exploited?: 1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.