CVE-2021-47068: net/nfc: fix use-after-free llcp_sock_bind/connect

Severity: high (CVSS 7.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2024-02-29 · updated 2026-06-17
Weakness: CWE-416

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.

Affected products

Linux kernel: from 4.4.267 before 4.4.269; from 4.9.267 before 4.9.269; from 4.14.231 before 4.14.233; from 4.19.187 before 4.19.191; from 5.4.112 before 5.4.119; from 5.10.30 before 5.10.37 — fixed in 4.14.233, 4.19.191, 4.4.269, 4.9.269, 5.10.37, 5.11.21

How to fix

Upgrade to a fixed version: Linux kernel 4.14.233, 4.19.191, 4.4.269, 4.9.269. Check the vendor advisory for mitigations.

References

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