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CVE-2026-72115
can: bcm: track a single source interface for ANYDEV timeout/throttle ops
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-2026-72115 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
An ANYDEV rx op (ifindex == 0) with an active RX timeout and/or throttle timer has no defined semantics when matching frames arrive from several interfaces: bcm_rx_handler() can run concurrently for the same op on different CPUs, racing hrtimer_cancel()/ bcm_rx_starttimer() against bcm_rx_timeout_handler() and causing spurious RX_TIMEOUT notifications and last_frames corruption. The same concurrency lets throttled multiplex frames from different interfaces clobber the single rx_ifindex/rx_stamp fields shared by the op. Add op->if_detected to track the first interface that delivers a matching frame while a timeout/throttle timer is configured, and reject frames from any other interface for that op. The claim is decided in bcm_rx_handler() before hrtimer_cancel() touches op->timer, so a rejected frame can never disturb the claimed interface's watchdog. RTR-mode ops are excluded via RX_RTR_FRAME, independent of kt_ival1/kt_ival2, since those may briefly hold a stale value from an earlier non-RTR configuration. The claim is released in bcm_notify() on NETDEV_UNREGISTER and in bcm_rx_setup() when SETTIMER reconfigures the timer values. A (re-)claim is only possible on CAN devices in NETREG_REGISTERED dev->reg_state to cover the release in bcm_notify() where reg_state becomes NETREG_UNREGISTERING until synchronize_net().
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
- 8.1 high
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:Nsource recompute it - Attack vector
- adjacent network (AV:A)source
- EPSS
- 0.30%, higher than 21.5% 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 |
|---|---|---|
| 2.6.25 | 5.10.265 | f147f48837cb |
| 2.6.25 | 5.15.216 | 57cf104da4cf |
| 2.6.25 | 6.1.183 | 03dfe347c398 |
| 2.6.25 | 6.6.148 | 18b45251e74e |
| 2.6.25 | 6.12.101 | 3ff8c24b4210 |
| 2.6.25 | 6.18.42 | eca8b44d51fc |
| 2.6.25 | 7.1.5 | b6317022b685 |
| 2.6.25 | 7.2 | 2f5976f54a04 |
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:AAttack vector, adjacent network
- bcm_rx_handler() is reached from the CAN driver RX path when matching frames arrive on multiple interfaces; on automotive/industrial systems an attacker on shared CAN segment(s) can inject concurrent frames without host shell access once an ANYDEV BCM RX op with active timeout/throttle timers exists.
- AC:LAttack complexity, low
- The attacker controls both sides of the race by flooding matching frames on multiple CAN interfaces (or paired vcan devices) to run bcm_rx_handler() concurrently on different CPUs, racing hrtimer_cancel/bcm_rx_starttimer against bcm_rx_timeout_handler and interleaved last_frames writers.
- PR:NPrivileges required, none
- No Linux capability or account is required to deliver triggering CAN traffic on multiple interfaces; bcm_rx_handler() runs from the unauthenticated netdev RX path once any ANYDEV BCM RX op with active kt_ival1/kt_ival2 timers exists, as commonly configured by telematics/diagnostic daemons.
- UI:NUser interaction, none
- Exploitation requires no victim interaction beyond normal system operation; malicious or concurrent CAN frames are processed automatically in softirq without mounts, file opens, or user prompts.
- S:UScope, unchanged
- Impact is confined to corrupted BCM state and incorrect CAN notifications delivered to the subscribing userspace process within the same kernel/host security boundary; no VM, container, or IOMMU escape is involved.
- C:HConfidentiality impact, high
- Concurrent bcm_rx_handler() and bcm_rx_timeout_handler() races corrupt op->last_frames heap buffers via unsynchronized memcpy/memset, mixing attacker-controlled CAN payloads from different interfaces and leaking cross-bus frame content through bcm_send_to_user().
- I:HIntegrity impact, high
- last_frames corruption lets attacker-controlled frames from one interface overwrite or interleave with another's stored/throttled state, misattributing RX_CHANGED/RX_TIMEOUT notifications and corrupting safety- or security-relevant CAN monitoring and control decisions.
- A:NAvailability impact, none
- The race corrupts per-op BCM buffers and emits spurious RX_TIMEOUT events but does not dereference freed objects, overrun buffer bounds, or fault the kernel; no oops, panic, hang, or sustained kernel denial of service is indicated.