---
id: CVE-2026-31474
title: 'can: isotp: fix tx.buf use-after-free in isotp_sendmsg()'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  can: isotp: fix tx.buf use-after-free in isotp_sendmsg()

  isotp_sendmsg() uses only cmpxchg() on so->tx.state to serialize access
  to so->tx.buf. isotp_release() waits f…
severity: high
cvss: 7.8
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H'
cvssSource: cna
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 96d1c81e6a0478535342dff6c730adb076cd84e8 <
    cb3d6efa78460e6d50bf68806d0db66265709f64
  - >-
    Linux >= 96d1c81e6a0478535342dff6c730adb076cd84e8 <
    9649d051e54413049c009638ec1dc23962c884a4
  - >-
    Linux >= 96d1c81e6a0478535342dff6c730adb076cd84e8 <
    eec8a1b18a79600bd4419079dc0026c1db72a830
  - >-
    Linux >= 96d1c81e6a0478535342dff6c730adb076cd84e8 <
    2e62e7051eca75a7f2e3d52d62ec10d7d7aa358c
  - >-
    Linux >= 96d1c81e6a0478535342dff6c730adb076cd84e8 <
    424e95d62110cdbc8fd12b40918f37e408e35a92
  - Linux 6.4
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: total
  timestamp: '2026-10-16T15:09:55.947236Z'
published: '2026-04-22'
updated: '2026-10-16'
sourceUpdated: '2026-10-16T15:20:12.522Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-31474'
references:
  - url: 'https://git.kernel.org/stable/c/cb3d6efa78460e6d50bf68806d0db66265709f64'
  - url: 'https://git.kernel.org/stable/c/9649d051e54413049c009638ec1dc23962c884a4'
  - url: 'https://git.kernel.org/stable/c/eec8a1b18a79600bd4419079dc0026c1db72a830'
  - url: 'https://git.kernel.org/stable/c/2e62e7051eca75a7f2e3d52d62ec10d7d7aa358c'
  - url: 'https://git.kernel.org/stable/c/424e95d62110cdbc8fd12b40918f37e408e35a92'
tags:
  - cve.org
epss: 0.00142
epssPercentile: 0.03102
ingestedAt: '2026-10-16T17:24:46.655Z'
---

## Overview

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

can: isotp: fix tx.buf use-after-free in isotp_sendmsg()

isotp_sendmsg() uses only cmpxchg() on so->tx.state to serialize access
to so->tx.buf. isotp_release() waits for ISOTP_IDLE via
wait_event_interruptible() and then calls kfree(so->tx.buf).

If a signal interrupts the wait_event_interruptible() inside close()
while tx.state is ISOTP_SENDING, the loop exits early and release
proceeds to force ISOTP_SHUTDOWN and continues to kfree(so->tx.buf)
while sendmsg may still be reading so->tx.buf for the final CAN frame
in isotp_fill_dataframe().

The so->tx.buf can be allocated once when the standard tx.buf length needs
to be extended. Move the kfree() of this potentially extended tx.buf to
sk_destruct time when either isotp_sendmsg() and isotp_release() are done.

## Affected

- `Linux >= 96d1c81e6a0478535342dff6c730adb076cd84e8 < cb3d6efa78460e6d50bf68806d0db66265709f64`
- `Linux >= 96d1c81e6a0478535342dff6c730adb076cd84e8 < 9649d051e54413049c009638ec1dc23962c884a4`
- `Linux >= 96d1c81e6a0478535342dff6c730adb076cd84e8 < eec8a1b18a79600bd4419079dc0026c1db72a830`
- `Linux >= 96d1c81e6a0478535342dff6c730adb076cd84e8 < 2e62e7051eca75a7f2e3d52d62ec10d7d7aa358c`
- `Linux >= 96d1c81e6a0478535342dff6c730adb076cd84e8 < 424e95d62110cdbc8fd12b40918f37e408e35a92`
- `Linux 6.4`

## Remediation

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