CVE-2026-72121 (GCVE-0-2026-72121)
Vulnerability from cvelistv5
Published
2026-08-15 05:52
Modified
2026-08-19 16:36
Severity ?
VLAI Severity ?
EPSS score ?
Summary
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.
References
Impacted products
| Vendor | Product | Version | ||
|---|---|---|---|---|
| Linux | Linux |
Version: 7595de7bc56e0e52b74e56c90f7e247bf626d628 Version: fbd8fdc2b218e979cfe422b139b8f74c12419d1f Version: 2a437b86ac5a9893c902f30ef66815bf13587bf6 Version: 76c84c3728178b2d38d5604e399dfe8b0752645e Version: cc55dd28c20a6611e30596019b3b2f636819a4c0 Version: c2aba69d0c36a496ab4f2e81e9c2b271f2693fd7 Version: c2aba69d0c36a496ab4f2e81e9c2b271f2693fd7 Version: c2aba69d0c36a496ab4f2e81e9c2b271f2693fd7 Version: 8f1c022541bf5a923c8d6fa483112c15250f30a4 Version: c4e8a172501e677ebd8ea9d9161d97dc4df56fbd Version: 5.10.238 ≤ Version: 5.15.185 ≤ Version: 6.1.141 ≤ Version: 6.6.93 ≤ Version: 6.12.31 ≤ Version: 5.4.294 ≤ Version: 6.14.9 ≤ |
||
{
"containers": {
"cna": {
"affected": [
{
"defaultStatus": "unaffected",
"product": "Linux",
"programFiles": [
"net/can/bcm.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
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"versionType": "git"
},
{
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"status": "affected",
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"versionType": "git"
},
{
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},
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},
{
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{
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},
{
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{
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},
{
"lessThan": "5.10.265",
"status": "affected",
"version": "5.10.238",
"versionType": "semver"
},
{
"lessThan": "5.15.216",
"status": "affected",
"version": "5.15.185",
"versionType": "semver"
},
{
"lessThan": "6.1.183",
"status": "affected",
"version": "6.1.141",
"versionType": "semver"
},
{
"lessThan": "6.6.148",
"status": "affected",
"version": "6.6.93",
"versionType": "semver"
},
{
"lessThan": "6.12.101",
"status": "affected",
"version": "6.12.31",
"versionType": "semver"
},
{
"lessThan": "5.5",
"status": "affected",
"version": "5.4.294",
"versionType": "semver"
},
{
"lessThan": "6.15",
"status": "affected",
"version": "6.14.9",
"versionType": "semver"
}
]
},
{
"defaultStatus": "affected",
"product": "Linux",
"programFiles": [
"net/can/bcm.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"status": "affected",
"version": "6.15"
},
{
"lessThan": "6.15",
"status": "unaffected",
"version": "0",
"versionType": "semver"
},
{
"lessThanOrEqual": "5.10.*",
"status": "unaffected",
"version": "5.10.265",
"versionType": "semver"
},
{
"lessThanOrEqual": "5.15.*",
"status": "unaffected",
"version": "5.15.216",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.1.*",
"status": "unaffected",
"version": "6.1.183",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.6.*",
"status": "unaffected",
"version": "6.6.148",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.12.*",
"status": "unaffected",
"version": "6.12.101",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.18.*",
"status": "unaffected",
"version": "6.18.42",
"versionType": "semver"
},
{
"lessThanOrEqual": "7.1.*",
"status": "unaffected",
"version": "7.1.5",
"versionType": "semver"
},
{
"lessThanOrEqual": "*",
"status": "unaffected",
"version": "7.2",
"versionType": "original_commit_for_fix"
}
]
}
],
"cpeApplicability": [
{
"nodes": [
{
"cpeMatch": [
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "5.10.265",
"versionStartIncluding": "5.10.238",
"vulnerable": true
},
{
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},
{
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},
{
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"versionEndExcluding": "6.6.148",
"versionStartIncluding": "6.6.93",
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},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.12.101",
"versionStartIncluding": "6.12.31",
"vulnerable": true
},
{
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"versionEndExcluding": "6.18.42",
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},
{
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"versionEndExcluding": "7.1.5",
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{
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},
{
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},
{
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}
],
"negate": false,
"operator": "OR"
}
]
}
],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\ncan: bcm: add locking when updating filter and timer values\n\nKCSAN detected a simultaneous access to timer values that can be\noverwritten in bcm_rx_setup() when updating timer and filter content\nwhile bcm_rx_handler(), bcm_rx_timeout_handler() or bcm_rx_thr_handler()\nrun concurrently on incoming CAN traffic.\n\nProtect the timer (ival1/ival2/kt_ival1/kt_ival2/kt_lastmsg) and filter\n(nframes/flags/frames/last_frames) updates in bcm_rx_setup() with a new\nper-op bcm_rx_update_lock, taken with the matching scope in the RX\nhandlers. memcpy_from_msg() is staged into a temporary buffer before the\nlock is taken, since it can sleep and must not run under a spinlock.\n\nhrtimer_cancel() is always called without bcm_rx_update_lock held, since\nbcm_rx_timeout_handler()/bcm_rx_thr_handler() take the same lock and a\nrunning callback would otherwise deadlock against the canceller.\n\nAlso close a related race: bcm_rx_setup() cleared the RTR flag in the\nstored reply frame\u0027s can_id as a separate, unprotected step after the\nframe content was already installed, so a concurrent bcm_rx_handler()\ncould transmit a stale reply with CAN_RTR_FLAG still set. Fold that\nnormalization into the initial frame preparation instead (on the staged\nbuffer for updates, directly on op-\u003eframes pre-registration for new\nops), so the installed frame is always atomically self-consistent.\n\nbcm_rx_handler()\u0027s RX_RTR_FRAME check now takes a lock-protected\nsnapshot of op-\u003eflags before deciding whether to call bcm_can_tx(),\nbut does not hold the lock across that call.\n\nAlso take a lock-protected snapshot of the currframe in bcm_can_tx()\nto avoid partly overwrites by content updates in bcm_tx_setup().\nFinally check if a TX_RESET_MULTI_IDX/SETTIMER might have reset\nop-\u003ecurrframe between the two locked sections in bcm_can_tx().\n\nOmit calling hrtimer_forward() with zero interval in bcm_rx_thr_handler().\nkt_ival2 may have been concurrently cleared by bcm_rx_setup() before it\ncancels this timer, so check kt_ival2 inside the bcm_rx_update_lock."
}
],
"metrics": [
{
"cvssV3_1": {
"baseScore": 8.8,
"baseSeverity": "HIGH",
"vectorString": "CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
"version": "3.1"
},
"scenarios": [
{
"lang": "en",
"value": "AV:A - The race is driven by concurrent CAN frame reception in bcm_rx_handler()/timer callbacks on a shared CAN segment (automotive OBD/ECU bus, factory controllers, CAN-USB adapters), an adjacent broadcast medium comparable to Bluetooth/WiFi segment access.\nAC:L - An attacker controls both race sides by flooding RX_SETUP via sendmsg while concurrently injecting matching CAN frames or armed timers; syzbot reliably reproduced the KCSAN race without timing conditions beyond attacker control.\nPR:N - CAN_BCM sockets impose no capability checks in can_create()/bcm_sendmsg(), and a bus participant can trigger the RX handler path without any Linux credentials while racing BCM configuration updates from local services.\nUI:N - Exploitation requires no victim interaction beyond normal background CAN/BCM activity on systems that already use the Broadcast Manager for monitoring or diagnostics.\nS:U - Impact is confined to kernel memory corruption and privilege boundaries within the same host; this is not a VM escape, IOMMU bypass, or cross-authority sandbox breakout.\nC:H - Unlocked concurrent updates to nframes/flags/frames/last_frames permit torn reads and out-of-bounds accesses in handler loops and timeout memset, matching the prior BCM race class that produced KASAN slab-out-of-bounds reads.\nI:H - Partial overwrites of op-\u003eframes during bcm_can_tx(), stale RTR replies transmitted on the bus, and size-mismatched memset/memcpy against concurrently shrinking buffers enable arbitrary CAN injection and kernel heap corruption.\nA:H - Concurrent timer corruption (hrtimer_forward with zero kt_ival2), torn structure fields, and heap corruption from racing memset/copy operations can cause kernel oops, panic, or sustained denial of service on CAN-equipped systems."
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-08-19T16:36:16.520Z",
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux"
},
"references": [
{
"url": "https://git.kernel.org/stable/c/96994180bd7b248b0cc698afe926e23fc1bda59b"
},
{
"url": "https://git.kernel.org/stable/c/caa8704a7f3cb7806331596195385437126ecb3a"
},
{
"url": "https://git.kernel.org/stable/c/a7c369e7da8203e2b5be12bbcac7b9ab2ed5b658"
},
{
"url": "https://git.kernel.org/stable/c/a7eb6db1cd3f7b556a301dc1265945ad112089f7"
},
{
"url": "https://git.kernel.org/stable/c/834cbca3b12e46887f7a9b35f1981a888360ea4c"
},
{
"url": "https://git.kernel.org/stable/c/19b1994069dd29478ba767de1f98f14a088198dc"
},
{
"url": "https://git.kernel.org/stable/c/fc9f5ee1b073bd233d9c604e338af4ebb42cbc33"
},
{
"url": "https://git.kernel.org/stable/c/749179c2e25b95d22499ed29096b3e02d6dfd2b4"
}
],
"title": "can: bcm: add locking when updating filter and timer values",
"x_generator": {
"engine": "bippy-1.2.0"
}
}
},
"cveMetadata": {
"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"assignerShortName": "Linux",
"cveId": "CVE-2026-72121",
"datePublished": "2026-08-15T05:52:59.959Z",
"dateReserved": "2026-08-09T03:40:39.907Z",
"dateUpdated": "2026-08-19T16:36:16.520Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
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Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
- Confirmed: The vulnerability is confirmed from an analyst perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: This vulnerability was exploited and seen by the user reporting the sighting.
- Patched: This vulnerability was successfully patched by the user reporting the sighting.
- Not exploited: This vulnerability was not exploited or seen by the user reporting the sighting.
- Not confirmed: The user expresses doubt about the veracity of the vulnerability.
- Not patched: This vulnerability was not successfully patched by the user reporting the sighting.
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