What’s Vulnerable › Vulnerabilities

CVE-2021-3640

• Severity: high (CVSS 7.0 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2022-03-03 · updated 2026-06-17
• Weakness: CWE-362

Description

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.

Affected products

• Canonical Ubuntu Linux: 14.04, 16.04, 18.04, 20.04, 21.10
• Debian Linux: 9.0
• Fedoraproject Fedora: 34
• Linux kernel: before 4.4.293; from 4.5 before 4.9.291; from 4.10 before 4.14.256; from 4.15 before 4.19.218; from 4.20 before 5.4.160; from 5.5.0 before 5.10.80 — fixed in 4.14.256, 4.19.218, 4.4.293, 4.9.291, 5.10.80, 5.14.19
• NetApp H300E Firmware: all versions
• NetApp H300S Firmware: all versions
• NetApp H410C Firmware: all versions
• NetApp H410S Firmware: all versions
• NetApp H500E Firmware: all versions
• NetApp H500S Firmware: all versions
• NetApp H700E Firmware: all versions
• NetApp H700S Firmware: all versions

How to fix

Upgrade to a fixed version: Linux kernel 4.14.256, 4.19.218, 4.4.293, 4.9.291. Check the vendor advisory for mitigations.

References

• https://bugzilla.redhat.com/show_bug.cgi?id=1980646
• https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/net/bluetooth/sco.c?h=v5.16&id=99c23da0eed4fd20cae8243f2b51e10e66aa0951
• https://github.com/torvalds/linux/commit/99c23da0eed4fd20cae8243f2b51e10e66aa0951
• https://lists.debian.org/debian-lts-announce/2022/03/msg00011.html
• https://lists.debian.org/debian-lts-announce/2022/03/msg00012.html
• https://security.netapp.com/advisory/ntap-20220419-0003/
• https://ubuntu.com/security/CVE-2021-3640
• https://www.debian.org/security/2022/dsa-5096
• https://www.openwall.com/lists/oss-security/2021/07/22/1
• https://bugzilla.redhat.com/show_bug.cgi?id=1980646
• https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/net/bluetooth/sco.c?h=v5.16&id=99c23da0eed4fd20cae8243f2b51e10e66aa0951
• https://github.com/torvalds/linux/commit/99c23da0eed4fd20cae8243f2b51e10e66aa0951

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