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CVE-2026-72126
can: isotp: use unconditional synchronize_rcu() in isotp_release()
Published 2026-08-15 (2 months ago) by the Linux kernel CNA. Subsystem net/can. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-72126 in every release this site tracks, and what each one means in practice. Every status below is the one the Debian Security Team publishes for this CVE. source
| Release | Status | Version | What this means |
|---|---|---|---|
| Debian 12bookworm | fixed | 6.1.180-1 | Update the kernel and reboot. Fixed in 6.1.180-1. A running kernel keeps the old code until the machine restarts. |
| Debian 13trixie | fixed | 6.12.100-1 | Update the kernel and reboot. Fixed in 6.12.100-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.1.5-1 | Update the kernel and reboot. Fixed in 7.1.5-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.1.5-1 | Update the kernel and reboot. Fixed in 7.1.5-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
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.
Where it lives
The fix touches these files. If the subsystem is one you do not use, the practical exposure is lower, though the package is still the vulnerable one.
net/can/isotp.c
- What this is
- CAN NETWORK LAYERMAINTAINERS section matched on net/can/ · linux-can@vger.kernel.org · Maintained
- Kernel module
- can_isotp
Check it on the machine
grep -wE 'CONFIG_CAN|CONFIG_CAN_ISOTP' /boot/config-$(uname -r)Reads the booted kernel's own configuration, on the machine and nowhere else. =y is built in, =m is a module, and an is not set line means the code is not there.
lsmod | grep -w can_isotpPrints a line if that module is loaded right now, and nothing if it is not. One that is not loaded can still be loaded later by anything that needs it.
Show whether Debian builds this, per release
Debian builds this, but not on every flavour. At least one release below builds the code on some of its kernel flavours and not on others, so the answer depends on the architecture and flavour installed.
- bookworm, trixie, forky, sidMnot built on amd64/cloud-amd64, arm64/cloud-arm64
- M
- a module where it is built at all; some flavours do not build it
- Build switches
- CONFIG_CAN, CONFIG_CAN_ISOTP
- Reads as
- all on means the file is compiled; any one off means it is not.
From the configuration Debian publishes for every kernel flavour it builds. It covers only the architectures Debian ships a linux-config package for, and nothing about a kernel you built yourself. Debian's own status above stays authoritative about the source package.MAINTAINERS kbuild Makefiles Debian linux-config packages
Signals
- Published
- 2026-08-15 (2 months ago)source
- CVSS
- 7.8 high
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:Hsource recompute it - Attack vector
- local (AV:L)source
- EPSS
- 0.17%, higher than 6.0% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- net/can
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 5.10.50 | 5.10.261 | 945d9894502c |
| 5.14 | 5.15.212 | 59672aa4bcd8 |
| 5.14 | 6.1.178 | 15413a082df6 |
| 5.14 | 6.6.145 | 6280eda96e07 |
| 5.14 | 6.12.97 | cb6abc584a1b |
| 5.14 | 6.18.40 | b88a51130877 |
| 5.14 | 7.1.5 | b8278ff60518 |
| 5.14 | 7.2 | 9b1a02e0d980 |
| 5.12.17 | 0 | 0 |
| 5.13.2 | 0 | 0 |
Why the CNA scored it this way
Quoted from the kernel CNA's own scoring file, word for word. A highlighted metric carries the most severe value CVSS v3.1 defines for it, which is what pushes the score up. source
- AV:LAttack vector, local
- The UAF is reached through local AF_CAN CAN_ISOTP socket syscalls (socket/bind/close) racing in-kernel ISO-TP RX; a CAN peer can deliver frames, but exploitation requires a local process to close the socket while NETDEV_UNREGISTER clears so->bound.
- AC:LAttack complexity, low
- The attacker controls all race sides: ISO-TP RX traffic via a local CAN socket or bus peer, concurrent close() on the ISOTP socket, and NETDEV_UNREGISTER by deleting the bound vcan/CAN interface (e.g., in a user namespace with CAP_NET_ADMIN).
- PR:LPrivileges required, low
- CAN_ISOTP socket create/bind/sendmsg/close paths impose no CAP_NET_ADMIN check; an unprivileged local user with access to a CAN netdev, including a user-namespace vcan they create, can reach the vulnerable release/timer path.
- UI:NUser interaction, none
- No victim interaction is required once the attacker can execute local code; they can open the ISO-TP socket, drive RX via CAN frames, delete the netdev, and close the socket to race isotp_rcv() against isotp_release().
- S:UScope, unchanged
- Exploitation corrupts kernel heap memory within the same OS security boundary (standard kernel UAF), not a VM/host or IOMMU sandbox escape.
- C:HConfidentiality impact, high
- Use-after-free of struct isotp_sock in isotp_rx_timer_handler reads freed memory (so->rx.state, sock fields), enabling heap grooming for arbitrary kernel memory disclosure per conservative UAF scoring guidance.
- I:HIntegrity impact, high
- The timer callback performs writes to fields within the freed isotp_sock/socket object, giving attacker-influenced kernel heap corruption that can be developed into arbitrary write or privilege-escalation primitives.
- A:HAvailability impact, high
- Executing isotp_rx_timer_handler on a freed socket can cause kernel oops/panic or fatal memory corruption; the UAF is reliably triggerable with attacker-controlled timing.