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 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.

Timeline

1. Apr 22, 2026, 1:54 PM UTCCVE published
2. Oct 16, 2026, 3:09 PM UTCCISA SSVC assessment

   Exploitation: none · Automatable: no · Technical impact: total

3. Oct 19, 2026, 6:35 PM UTCRecord last updated

Affected versions

• Linux Linux

  From 96d1c81e6a0478535342dff6c730adb076cd84e8 · fixed in cb3d6efa78460e6d50bf68806d0db66265709f64; From 96d1c81e6a0478535342dff6c730adb076cd84e8 · fixed in 9649d051e54413049c009638ec1dc23962c884a4; From 96d1c81e6a0478535342dff6c730adb076cd84e8 · fixed in eec8a1b18a79600bd4419079dc0026c1db72a830; From 96d1c81e6a0478535342dff6c730adb076cd84e8 · fixed in 2e62e7051eca75a7f2e3d52d62ec10d7d7aa358c; From 96d1c81e6a0478535342dff6c730adb076cd84e8 · fixed in 424e95d62110cdbc8fd12b40918f37e408e35a92

• Linux Linux

  6.4

• KernelLinux

  From 6.4.0 · fixed in 6.6.131; From 6.7.0 · fixed in 6.12.80; From 6.13.0 · fixed in 6.18.21; From 6.19.0 · fixed in 6.19.11

References 5