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CVE-2026-72114
can: bcm: validate frame length in bcm_rx_setup() for RTR replies
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-2026-72114 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
bcm_tx_setup() validates cf->len against the CAN/CAN FD DLC limits before installing frames for TX_SETUP, but bcm_rx_setup() never did the same for the RTR-reply frame configured via RX_SETUP with RX_RTR_FRAME.
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 |
|---|---|---|
| 2.6.25 | 5.10.265 | cc1f9569f1c1 |
| 2.6.25 | 5.15.216 | 204f2b232717 |
| 2.6.25 | 6.1.183 | e061624c0a86 |
| 2.6.25 | 6.6.148 | 7d966cdee006 |
| 2.6.25 | 6.12.101 | 1b475c0c72f4 |
| 2.6.25 | 6.18.42 | deb6a697cce3 |
| 2.6.25 | 7.1.5 | 59bfddea6415 |
| 2.6.25 | 7.2 | 62ec41f36464 |
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 missing validation is in bcm_rx_setup(), reached only via local PF_CAN SOCK_DGRAM CAN_BCM syscalls (socket/connect/sendmsg RX_SETUP with RX_RTR_FRAME); it is not triggered by remote IP services or by CAN bus traffic alone.
- AC:LAttack complexity, low
- An attacker reliably installs a malformed RTR-reply frame with a single RX_SETUP sendmsg and can trigger bcm_can_tx() by sending or waiting for a matching RTR on the bound interface, with no races or layout dependencies beyond their control.
- PR:LPrivileges required, low
- can_create(), bcm_connect(), and bcm_sendmsg() perform no capability checks; any local user with access to a CAN interface (including vcan created with CAP_NET_ADMIN in an unprivileged user namespace) can open BCM sockets and program RX_SETUP RTR replies.
- UI:NUser interaction, none
- Exploitation requires only the attacker opening a BCM socket and sending RX_SETUP messages; no victim interaction such as mounting filesystems or opening files is needed once local CAN access exists.
- S:UScope, unchanged
- Impact is kernel memory corruption and unauthorized CAN frame transmission within the same host security domain; it does not cross VM, container, or IOMMU boundaries even when frames reach an adjacent vehicle or industrial CAN segment.
- C:HConfidentiality impact, high
- Unvalidated cf->len values are stored in op->frames and later passed to bcm_can_tx()/can_send(); many CAN driver ndo_start_xmit paths memcpy(cf->data, cf->len) trusting len, enabling out-of-bounds kernel reads when invalid lengths bypass or race skb validation.
- I:HIntegrity impact, high
- Attacker-controlled len in the RTR-reply frame can drive out-of-bounds memcpy writes in CAN USB/SPI/hardware xmit paths and inject attacker-crafted frame payloads onto safety-critical automotive, factory, or embedded CAN buses when RTR requests are answered.
- A:HAvailability impact, high
- Out-of-bounds accesses in CAN driver transmit paths from trusted-but-invalid len values can cause kernel WARN/Oops/panic on hardened builds, and repeated malformed RTR-reply transmission attempts can wedge TX queues or disrupt CAN service on affected systems.