What is CVE-2021-3640?

CVE-2021-3640 is a high-severity vulnerability in Linux Kernel, classified under Concurrent Execution using Shared Resource with Improper Synchronization (Race Condition). CVSS score: 7.0/10. Published 2022-03-03.

How severe is CVE-2021-3640?

High severity. CVSS v3 base score is 7.0 out of 10.

Is CVE-2021-3640 known to be exploited?

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

Use After Free in Linux Kernel

CVE-2021-3640

A flaw use-after-free in function sco_sock_sendmsg() of the Linux kernel HCI subsystem was found in the way user calls ioct UFFDIO_REGISTER or other way triggers race condition of the call sco_conn_del() together with the call sco_sock_sendmsg() with the expected controllable faulting memory page. A privileged local user could use this flaw to crash the system or escalate their privileges on the system.

Vulnerability class: Race Condition

Published 2022-03-03 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 7.0 (High). Vector: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.004 (28.5th percentile), scored 2026-10-02.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 29th percentile — 28.5% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.004 · newest: 0.004 · change: 0.000

Affected products

Weakness classification (CWE)

Public proof-of-concept exploits

ARPSyndicate/cvemon

References

bugzilla.redhat.com/show_bug.cgi (Patch, Third Party Advisory, Issue Tracking)
ubuntu.com/security/CVE-2021-3640 (Patch, Third Party Advisory)
www.openwall.com/lists/oss-security/2021/07/22/1 (Exploit, Mailing List, Third Party Advisory)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/net/bluetooth… (Patch, Vendor Advisory)
github.com/torvalds/linux/commit/99c23da0eed4fd20cae8243f2b51e10e66aa0951 (Patch, Third Party Advisory)
lists.debian.org/debian-lts-announce/2022/03/msg00011.html (mailing-list, Mailing List, Third Party Advisory)
lists.debian.org/debian-lts-announce/2022/03/msg00012.html (mailing-list, Mailing List, Third Party Advisory)
www.debian.org/security/2022/dsa-5096 (vendor-advisory, Third Party Advisory)
security.netapp.com/advisory/ntap-20220419-0003/ (Third Party Advisory)

Frequently asked questions

What is CVE-2021-3640?: CVE-2021-3640 is a high-severity vulnerability in Linux Kernel, classified under Concurrent Execution using Shared Resource with Improper Synchronization (Race Condition). CVSS score: 7.0/10. Published 2022-03-03.
How severe is CVE-2021-3640?: High severity. CVSS v3 base score is 7.0 out of 10.
Is CVE-2021-3640 known to be exploited?: 1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.