Linux Kernel up to 7.2-rc3 CAN BCM bcm_rx_setup race condition

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8.4	$0-$5k	0.00-

Summaryinfo

A vulnerability marked as very critical has been reported in Linux Kernel up to 6.6.147/6.12.100/6.18.41/7.1.4/7.2-rc3. The affected element is the function bcm_rx_setup of the component CAN BCM. This manipulation of the argument ival1/ival2/kt_ival1/kt_ival2/kt_lastmsg/nframes/flags/frames/last_frames causes race condition. This vulnerability appears as CVE-2026-72121. The attack requires local access. There is no available exploit.

Detailsinfo

A vulnerability classified as very critical was found in Linux Kernel up to 6.6.147/6.12.100/6.18.41/7.1.4/7.2-rc3. Affected by this vulnerability is the function bcm_rx_setup of the component CAN BCM. The manipulation of the argument ival1/ival2/kt_ival1/kt_ival2/kt_lastmsg/nframes/flags/frames/last_frames with an unknown input leads to a race condition vulnerability. The CWE definition for the vulnerability is CWE-362. The product contains a code sequence that can run concurrently with other code, and the code sequence requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence that is operating concurrently. As an impact it is known to affect confidentiality, integrity, and availability. The summary by CVE is:

In the Linux kernel, the following vulnerability has been resolved: can: bcm: add locking when updating filter and timer values KCSAN detected a simultaneous access to timer values that can be overwritten in bcm_rx_setup() when updating timer and filter content while bcm_rx_handler(), bcm_rx_timeout_handler() or bcm_rx_thr_handler() run concurrently on incoming CAN traffic. Protect the timer (ival1/ival2/kt_ival1/kt_ival2/kt_lastmsg) and filter (nframes/flags/frames/last_frames) updates in bcm_rx_setup() with a new per-op bcm_rx_update_lock, taken with the matching scope in the RX handlers. memcpy_from_msg() is staged into a temporary buffer before the lock is taken, since it can sleep and must not run under a spinlock. hrtimer_cancel() is always called without bcm_rx_update_lock held, since bcm_rx_timeout_handler()/bcm_rx_thr_handler() take the same lock and a running callback would otherwise deadlock against the canceller. Also close a related race: bcm_rx_setup() cleared the RTR flag in the stored reply frame's can_id as a separate, unprotected step after the frame content was already installed, so a concurrent bcm_rx_handler() could transmit a stale reply with CAN_RTR_FLAG still set. Fold that normalization into the initial frame preparation instead (on the staged buffer for updates, directly on op->frames pre-registration for new ops), so the installed frame is always atomically self-consistent. bcm_rx_handler()'s RX_RTR_FRAME check now takes a lock-protected snapshot of op->flags before deciding whether to call bcm_can_tx(), but does not hold the lock across that call. Also take a lock-protected snapshot of the currframe in bcm_can_tx() to avoid partly overwrites by content updates in bcm_tx_setup(). Finally check if a TX_RESET_MULTI_IDX/SETTIMER might have reset op->currframe between the two locked sections in bcm_can_tx(). Omit calling hrtimer_forward() with zero interval in bcm_rx_thr_handler(). kt_ival2 may have been concurrently cleared by bcm_rx_setup() before it cancels this timer, so check kt_ival2 inside the bcm_rx_update_lock.

It is possible to read the advisory at git.kernel.org. This vulnerability is known as CVE-2026-72121 since 08/09/2026. The exploitation appears to be easy. Attacking locally is a requirement. Technical details of the vulnerability are known, but there is no available exploit. The pricing for an exploit might be around USD $0-$5k at the moment (estimation calculated on 08/15/2026).

Upgrading to version 6.6.148, 6.12.101, 6.18.42, 7.1.5 or 7.2-rc4 eliminates this vulnerability. Applying the patch a7eb6db1cd3f7b556a301dc1265945ad112089f7/834cbca3b12e46887f7a9b35f1981a888360ea4c/19b1994069dd29478ba767de1f98f14a088198dc/fc9f5ee1b073bd233d9c604e338af4ebb42cbc33/749179c2e25b95d22499ed29096b3e02d6dfd2b4 is able to eliminate this problem.

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Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 6.0
• 6.1
• 6.2
• 6.3
• 6.4
• 6.5
• 6.6
• 6.6.147
• 6.7
• 6.8
• 6.9
• 6.10
• 6.11
• 6.12.100
• 6.18.0
• 6.18.1
• 6.18.2
• 6.18.3
• 6.18.4
• 6.18.5
• 6.18.6
• 6.18.7
• 6.18.8
• 6.18.9
• 6.18.10
• 6.18.11
• 6.18.12
• 6.18.13
• 6.18.14
• 6.18.15
• 6.18.16
• 6.18.17
• 6.18.18
• 6.18.19
• 6.18.20
• 6.18.21
• 6.18.22
• 6.18.23
• 6.18.24
• 6.18.25
• 6.18.26
• 6.18.27
• 6.18.28
• 6.18.29
• 6.18.30
• 6.18.31
• 6.18.32
• 6.18.33
• 6.18.34
• 6.18.35
• 6.18.36
• 6.18.37
• 6.18.38
• 6.18.39
• 6.18.40
• 6.18.41
• 7.1.0
• 7.1.1
• 7.1.2
• 7.1.3
• 7.1.4
• 7.2-rc1
• 7.2-rc2
• 7.2-rc3

License

• open-source

Website

• Vendor: https://www.kernel.org/

CPE 2.3info

• 🔒
• 🔒
• 🔒

CPE 2.2info

• 🔒
• 🔒
• 🔒

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 8.8
VulDB Meta Temp Score: 8.4

VulDB Base Score: 8.8
VulDB Temp Score: 8.4
VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv2info

AV	AC	Au	C	I	A
💳	💳	💳	💳	💳	💳
💳	💳	💳	💳	💳	💳
💳	💳	💳	💳	💳	💳

Vector	Complexity	Authentication	Confidentiality	Integrity	Availability
Unlock	Unlock	Unlock	Unlock	Unlock	Unlock
Unlock	Unlock	Unlock	Unlock	Unlock	Unlock
Unlock	Unlock	Unlock	Unlock	Unlock	Unlock

VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Race condition
CWE: CWE-362
CAPEC: 🔒
ATT&CK: 🔒

Physical: Partially
Local: Yes
Remote: No

Availability: 🔒
Status: Not defined

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

0-Day	Unlock	Unlock	Unlock	Unlock
Today	Unlock	Unlock	Unlock	Unlock

Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: Kernel 6.6.148/6.12.101/6.18.42/7.1.5/7.2-rc4
Patch: a7eb6db1cd3f7b556a301dc1265945ad112089f7/834cbca3b12e46887f7a9b35f1981a888360ea4c/19b1994069dd29478ba767de1f98f14a088198dc/fc9f5ee1b073bd233d9c604e338af4ebb42cbc33/749179c2e25b95d22499ed29096b3e02d6dfd2b4

Timelineinfo

08/09/2026 CVE reserved
08/15/2026 +6 days Advisory disclosed
08/15/2026 +0 days VulDB entry created
08/15/2026 +0 days VulDB entry last update

Sourcesinfo

Vendor: kernel.org

Advisory: git.kernel.org
Status: Confirmed

CVE: CVE-2026-72121 (🔒)
GCVE (CVE): GCVE-0-2026-72121
GCVE (VulDB): GCVE-100-390583

Entryinfo

Created: 08/15/2026 13:03
Changes: 08/15/2026 13:03 (60)
Complete: 🔍
Cache ID: 216::103

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Discussion

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