---
id: CVE-2026-64541
title: 'net/smc: fix UAF in smc_cdc_rx_handler() by pinning the socket'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  net/smc: fix UAF in smc_cdc_rx_handler() by pinning the socket

  smc_cdc_rx_handler() looks up the connection by token under the link
  group's conns_lock, drops the lock,…
severity: critical
cvss: 9.8
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H'
cvssSource: cna
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= d7b0e37c1ac152905b18a5b9506179091a35b0b6 <
    8de4f665d0febfb92803dece377791a563fc7041
  - >-
    Linux >= d7b0e37c1ac152905b18a5b9506179091a35b0b6 <
    8145b432136285e01091815b48ceb2dae261f262
  - >-
    Linux >= d7b0e37c1ac152905b18a5b9506179091a35b0b6 <
    1951bffbc6493ec34cff3956b29d4bc6606904a6
  - >-
    Linux >= d7b0e37c1ac152905b18a5b9506179091a35b0b6 <
    647b19e5cc145a2f1f685ae8ff3805a17356888c
  - >-
    Linux >= d7b0e37c1ac152905b18a5b9506179091a35b0b6 <
    472e9d7c0d5b03be3ff91ff941f57da822b031bc
  - >-
    Linux >= d7b0e37c1ac152905b18a5b9506179091a35b0b6 <
    3bfb96d9bc6a7ed0b99c7db329cc2e22a28d84bb
  - >-
    Linux >= d7b0e37c1ac152905b18a5b9506179091a35b0b6 <
    ce5aa8084329351086894aa34d77e40301d5bd3d
  - >-
    Linux >= d7b0e37c1ac152905b18a5b9506179091a35b0b6 <
    9d160b35cc34a2ba8229d07651468a7848325135
  - Linux 4.18
ssvc:
  exploitation: none
  automatable: 'yes'
  technicalImpact: total
  timestamp: '2026-10-16T15:42:09.809089Z'
published: '2026-07-27'
updated: '2026-10-16'
sourceUpdated: '2026-10-16T15:52:51.153Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-64541'
references:
  - url: 'https://git.kernel.org/stable/c/8de4f665d0febfb92803dece377791a563fc7041'
  - url: 'https://git.kernel.org/stable/c/8145b432136285e01091815b48ceb2dae261f262'
  - url: 'https://git.kernel.org/stable/c/1951bffbc6493ec34cff3956b29d4bc6606904a6'
  - url: 'https://git.kernel.org/stable/c/647b19e5cc145a2f1f685ae8ff3805a17356888c'
  - url: 'https://git.kernel.org/stable/c/472e9d7c0d5b03be3ff91ff941f57da822b031bc'
  - url: 'https://git.kernel.org/stable/c/3bfb96d9bc6a7ed0b99c7db329cc2e22a28d84bb'
  - url: 'https://git.kernel.org/stable/c/ce5aa8084329351086894aa34d77e40301d5bd3d'
  - url: 'https://git.kernel.org/stable/c/9d160b35cc34a2ba8229d07651468a7848325135'
tags:
  - cve.org
epss: 0.00565
epssPercentile: 0.45729
ingestedAt: '2026-10-16T17:24:46.830Z'
---

## Overview

In the Linux kernel, the following vulnerability has been resolved:

net/smc: fix UAF in smc_cdc_rx_handler() by pinning the socket

smc_cdc_rx_handler() looks up the connection by token under the link
group's conns_lock, drops the lock, and then dereferences conn and the
smc_sock derived from it, ending in sock_hold(&smc->sk) inside
smc_cdc_msg_recv(). No reference is held across the lock release.

The only reference pinning the socket while the connection is
discoverable in the link group is taken in smc_lgr_register_conn()
(sock_hold) and dropped in __smc_lgr_unregister_conn() (sock_put), both
under conns_lock. Once the handler drops conns_lock, a concurrent
close() -> smc_release() -> smc_conn_free() -> smc_lgr_unregister_conn()
can drop that reference and free the smc_sock, so the handler's later
sock_hold() runs on freed memory:

  WARNING: lib/refcount.c:25 at refcount_warn_saturate
  Workqueue: rxe_wq do_work
   refcount_warn_saturate (lib/refcount.c:25)
   smc_cdc_msg_recv (net/smc/smc_cdc.c:430)
   smc_cdc_rx_handler (net/smc/smc_cdc.c:502)
   smc_wr_rx_tasklet_fn (net/smc/smc_wr.c:445)
   tasklet_action_common (kernel/softirq.c:938)
   handle_softirqs (kernel/softirq.c:622)
  Kernel panic - not syncing: panic_on_warn set

Only SMC-R is affected. The SMC-D receive tasklet is stopped by
tasklet_kill(&conn->rx_tsklet) in smc_conn_free() before the connection
is unregistered, so it cannot run concurrently with the free.

Take the socket reference while still holding conns_lock, so the
registration reference can no longer be the last one, and drop it once
the handler is done.

## Affected

- `Linux >= d7b0e37c1ac152905b18a5b9506179091a35b0b6 < 8de4f665d0febfb92803dece377791a563fc7041`
- `Linux >= d7b0e37c1ac152905b18a5b9506179091a35b0b6 < 8145b432136285e01091815b48ceb2dae261f262`
- `Linux >= d7b0e37c1ac152905b18a5b9506179091a35b0b6 < 1951bffbc6493ec34cff3956b29d4bc6606904a6`
- `Linux >= d7b0e37c1ac152905b18a5b9506179091a35b0b6 < 647b19e5cc145a2f1f685ae8ff3805a17356888c`
- `Linux >= d7b0e37c1ac152905b18a5b9506179091a35b0b6 < 472e9d7c0d5b03be3ff91ff941f57da822b031bc`
- `Linux >= d7b0e37c1ac152905b18a5b9506179091a35b0b6 < 3bfb96d9bc6a7ed0b99c7db329cc2e22a28d84bb`
- `Linux >= d7b0e37c1ac152905b18a5b9506179091a35b0b6 < ce5aa8084329351086894aa34d77e40301d5bd3d`
- `Linux >= d7b0e37c1ac152905b18a5b9506179091a35b0b6 < 9d160b35cc34a2ba8229d07651468a7848325135`
- `Linux 4.18`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.