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CVE-2026-72119
can: bcm: extend bcm_tx_lock usage for data and timer updates
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-2026-72119 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 | fixedDLA-4777-1 · 2026-09-08 · text | 6.1.187-1 | Update the kernel and reboot. DLA-4777-1 shipped the fix on 2026-09-08, in 6.1.187-1. A running kernel keeps the old code until the machine restarts. |
| Debian 13trixie | fixed | 6.12.101-1 | Update the kernel and reboot. Fixed in 6.12.101-1. 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. |
| Debian 12bookworm · linux-6.12 | fixedDLA-4745-1 · 2026-08-18 · text | 6.12.101-1~deb12u1 | Update the kernel and reboot. DLA-4745-1 shipped the fix on 2026-08-18, in 6.12.101-1~deb12u1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
Stage new CAN frame content for an existing tx op into a kmalloc()'d buffer and validate it there, mirroring the approach already used in bcm_rx_setup(). Only copy the validated data into op->frames while holding op->bcm_tx_lock, so bcm_can_tx() and bcm_tx_timeout_handler() can no longer observe a partially updated or unvalidated frame. Add a missing error path for memcpy_from_msg() when copying CAN frame data from userspace. Also move the kt_ival1/kt_ival2/ival1/ival2 updates in bcm_tx_setup() under op->bcm_tx_lock, and read kt_ival1/kt_ival2/count under the same lock in bcm_tx_set_expiry() and bcm_tx_timeout_handler(), closing the torn 64-bit ktime_t read on 32-bit platforms.
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/bcm.c
- What this is
- CAN NETWORK LAYERMAINTAINERS section matched on net/can/ · linux-can@vger.kernel.org · Maintained
- Kernel module
- can_bcm
Check it on the machine
grep -wE 'CONFIG_CAN|CONFIG_CAN_BCM' /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_bcmPrints 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, sid, bookworm · linux-6.12Mnot 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_BCM
- 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 5.8% 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 |
|---|---|---|
| 5.10.238 | 5.10.265 | a538b072ee07 |
| 5.15.185 | 5.15.216 | 63422347b4c7 |
| 6.1.141 | 6.1.183 | 37917e432e50 |
| 6.6.93 | 6.6.148 | 52f06e760378 |
| 6.12.31 | 6.12.101 | 972fd66bb08f |
| 6.15 | 6.18.42 | bd46f55dec60 |
| 6.15 | 7.1.5 | 337f966c0066 |
| 6.15 | 7.2 | 12ce799f7ab1 |
| 5.4.294 | 0 | 0 |
| 6.14.9 | 0 | 0 |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4777-1 | 2026-09-08 | bookworm 6.1.187-1 | tracker |
| DLA-4745-1 | 2026-08-18 | bookworm 6.12.101-1~deb12u1 | tracker |
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 bug is reached only through PF_CAN/CAN_BCM socket sendmsg() TX_SETUP updates racing hrtimer-driven bcm_can_tx(); it is not triggered by remote network services or CAN bus traffic alone.
- AC:LAttack complexity, low
- The attacker controls both sides of the race by creating cyclic TX ops with STARTTIMER/SETTIMER and repeatedly issuing TX_SETUP while the softirq hrtimer fires, making the window reliably winnable without external timing luck.
- PR:LPrivileges required, low
- bcm_sendmsg()/bcm_connect() enforce no capability checks; any local user with access to a CAN interface (including vcan created with CAP_NET_ADMIN inside an unprivileged user namespace) can open BCM sockets and drive TX_SETUP.
- UI:NUser interaction, none
- Exploitation requires only the attacker opening a BCM socket and sending TX_SETUP messages; no victim interaction such as mounting filesystems or opening files is needed.
- S:UScope, unchanged
- Impact is confined to kernel memory/state corruption and local privilege effects on the host running CAN BCM; it does not cross a VM, container, or IOMMU security boundary by itself.
- C:HConfidentiality impact, high
- Racing updates can let bcm_can_tx() transmit partially updated or unvalidated frames (e.g., len>64) before bcm_tx_setup() rejects them, and many CAN driver xmit paths memcpy(cf->data, cf->len) trusting len, causing kernel out-of-bounds reads.
- I:HIntegrity impact, high
- Concurrent unsynchronized writes to op->frames, flags, count, and ktime_t timer fields corrupt shared in-kernel BCM state that directly feeds skb construction and driver transmission, providing attacker-influenced memory corruption primitives.
- A:HAvailability impact, high
- Observing torn/unvalidated frames in bcm_can_tx() during active timers can trigger kernel WARN/Oops/panic via out-of-bounds accesses in CAN drivers, and torn ktime_t/count reads can disrupt cyclic transmission causing denial of service.