FKIE_CVE-2026-93287
Vulnerability from fkie_nvd - Published: 2026-09-24 17:17 - Updated: 2026-09-25 05:17
Severity
Summary
In the Linux kernel, the following vulnerability has been resolved:
i2c: smbus: reject oversized block transfers in the common path
The SMBus block transfer length data->block[0] is validated in
i2c_smbus_xfer_emulated() but that check runs too late for tracepoints
and is skipped entirely when the adapter provides a native smbus_xfer
implementation. This allows user-controlled oversized block lengths to
reach tracepoint memcpy calls and driver callbacks unchecked.
Add an early validation in __i2c_smbus_xfer() that rejects block
transfers whose caller-supplied length is zero or exceeds
I2C_SMBUS_BLOCK_MAX before any tracepoint fires or driver callback
runs. data->block[0] is filled in by the device on SMBus block reads,
so the check is scoped to operations where the length is actually
supplied by the caller. This is consistent with the existing -EINVAL
convention in the emulated path and protects all downstream consumers
at once: the smbus_write tracepoint, all native smbus_xfer driver
implementations, and the emulated path.
Two distinct bugs are fixed by this change:
Bug 1: smbus_write tracepoint OOB (include/trace/events/smbus.h)
trace_smbus_write() fires before any validation and copies
data->block[0]+1 bytes into a 34-byte event buffer. With
block[0]=0xfe the tracepoint copies 255 bytes, overflowing by 221.
BUG: KASAN: stack-out-of-bounds in trace_event_raw_event_smbus_write+0x27c/0x530
Read of size 255 at addr ffff88800d98fcf8 by task poc_smbus/91
Call Trace:
<TASK>
__asan_memcpy+0x23/0x80
trace_event_raw_event_smbus_write+0x27c/0x530
__i2c_smbus_xfer+0x43a/0xa40
i2c_smbus_xfer+0x19e/0x340
i2cdev_ioctl_smbus+0x38f/0x7f0
i2cdev_ioctl+0x35e/0x680
__x64_sys_ioctl+0x147/0x1e0
do_syscall_64+0xcf/0x15a0
entry_SYSCALL_64_after_hwframe+0x76/0x7e
</TASK>
Bug 2: i2c-stub I2C_SMBUS_I2C_BLOCK_DATA OOB (drivers/i2c/i2c-stub.c)
stub_xfer() implements .smbus_xfer directly and only clamps
block[0] against 256-command, not I2C_SMBUS_BLOCK_MAX. With
block[0]=0xff and command=0 the loop accesses block[1+i] for
i up to 254, far past the 34-byte union.
UBSAN: array-index-out-of-bounds in drivers/i2c/i2c-stub.c:223:44
index 34 is out of range for type '__u8 [34]'
Call Trace:
<TASK>
__ubsan_handle_out_of_bounds+0xd7/0x120
stub_xfer+0x1971/0x198f [i2c_stub]
__i2c_smbus_xfer+0x306/0xa40
i2c_smbus_xfer+0x19e/0x340
i2cdev_ioctl_smbus+0x38f/0x7f0
i2cdev_ioctl+0x35e/0x680
__x64_sys_ioctl+0x147/0x1e0
do_syscall_64+0xcf/0x15a0
entry_SYSCALL_64_after_hwframe+0x76/0x7e
</TASK>
Both traces reproduced on v7.0-rc6+i2c/for-current with KASAN+UBSAN.
References
Impacted products
| Vendor | Product | Version |
|---|
{
"affected": [
{
"affectedData": [
{
"defaultStatus": "unaffected",
"product": "Linux",
"programFiles": [
"drivers/i2c/i2c-core-smbus.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"lessThan": "f09edffba97d37b1fdff5f818a9a45f8a98ac171",
"status": "affected",
"version": "4710317891e4824ce1510a6b5066abbd3e917750",
"versionType": "git"
},
{
"lessThan": "c4b478bc50b7ca9865e237909941253a0f7111a2",
"status": "affected",
"version": "4710317891e4824ce1510a6b5066abbd3e917750",
"versionType": "git"
},
{
"lessThan": "3051cd060fa496df42954291fa2306ed2eab4ecc",
"status": "affected",
"version": "4710317891e4824ce1510a6b5066abbd3e917750",
"versionType": "git"
}
]
},
{
"defaultStatus": "affected",
"product": "Linux",
"programFiles": [
"drivers/i2c/i2c-core-smbus.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"status": "affected",
"version": "2.6.33"
},
{
"lessThan": "2.6.33",
"status": "unaffected",
"version": "0",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.12.*",
"status": "unaffected",
"version": "6.12.111",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.18.*",
"status": "unaffected",
"version": "6.18.53",
"versionType": "semver"
},
{
"lessThanOrEqual": "*",
"status": "unaffected",
"version": "7.1",
"versionType": "original_commit_for_fix"
}
]
}
],
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}
],
"cveTags": [],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\ni2c: smbus: reject oversized block transfers in the common path\n\nThe SMBus block transfer length data-\u003eblock[0] is validated in\ni2c_smbus_xfer_emulated() but that check runs too late for tracepoints\nand is skipped entirely when the adapter provides a native smbus_xfer\nimplementation. This allows user-controlled oversized block lengths to\nreach tracepoint memcpy calls and driver callbacks unchecked.\n\nAdd an early validation in __i2c_smbus_xfer() that rejects block\ntransfers whose caller-supplied length is zero or exceeds\nI2C_SMBUS_BLOCK_MAX before any tracepoint fires or driver callback\nruns. data-\u003eblock[0] is filled in by the device on SMBus block reads,\nso the check is scoped to operations where the length is actually\nsupplied by the caller. This is consistent with the existing -EINVAL\nconvention in the emulated path and protects all downstream consumers\nat once: the smbus_write tracepoint, all native smbus_xfer driver\nimplementations, and the emulated path.\n\nTwo distinct bugs are fixed by this change:\n\nBug 1: smbus_write tracepoint OOB (include/trace/events/smbus.h)\n trace_smbus_write() fires before any validation and copies\n data-\u003eblock[0]+1 bytes into a 34-byte event buffer. With\n block[0]=0xfe the tracepoint copies 255 bytes, overflowing by 221.\n\n BUG: KASAN: stack-out-of-bounds in trace_event_raw_event_smbus_write+0x27c/0x530\n Read of size 255 at addr ffff88800d98fcf8 by task poc_smbus/91\n Call Trace:\n \u003cTASK\u003e\n __asan_memcpy+0x23/0x80\n trace_event_raw_event_smbus_write+0x27c/0x530\n __i2c_smbus_xfer+0x43a/0xa40\n i2c_smbus_xfer+0x19e/0x340\n i2cdev_ioctl_smbus+0x38f/0x7f0\n i2cdev_ioctl+0x35e/0x680\n __x64_sys_ioctl+0x147/0x1e0\n do_syscall_64+0xcf/0x15a0\n entry_SYSCALL_64_after_hwframe+0x76/0x7e\n \u003c/TASK\u003e\n\nBug 2: i2c-stub I2C_SMBUS_I2C_BLOCK_DATA OOB (drivers/i2c/i2c-stub.c)\n stub_xfer() implements .smbus_xfer directly and only clamps\n block[0] against 256-command, not I2C_SMBUS_BLOCK_MAX. With\n block[0]=0xff and command=0 the loop accesses block[1+i] for\n i up to 254, far past the 34-byte union.\n\n UBSAN: array-index-out-of-bounds in drivers/i2c/i2c-stub.c:223:44\n index 34 is out of range for type \u0027__u8 [34]\u0027\n Call Trace:\n \u003cTASK\u003e\n __ubsan_handle_out_of_bounds+0xd7/0x120\n stub_xfer+0x1971/0x198f [i2c_stub]\n __i2c_smbus_xfer+0x306/0xa40\n i2c_smbus_xfer+0x19e/0x340\n i2cdev_ioctl_smbus+0x38f/0x7f0\n i2cdev_ioctl+0x35e/0x680\n __x64_sys_ioctl+0x147/0x1e0\n do_syscall_64+0xcf/0x15a0\n entry_SYSCALL_64_after_hwframe+0x76/0x7e\n \u003c/TASK\u003e\n\nBoth traces reproduced on v7.0-rc6+i2c/for-current with KASAN+UBSAN."
}
],
"id": "CVE-2026-93287",
"lastModified": "2026-09-25T05:17:02.023",
"metrics": {
"cvssMetricV31": [
{
"cvssData": {
"attackComplexity": "LOW",
"attackVector": "LOCAL",
"availabilityImpact": "HIGH",
"baseScore": 7.8,
"baseSeverity": "HIGH",
"confidentialityImpact": "HIGH",
"integrityImpact": "HIGH",
"privilegesRequired": "LOW",
"scope": "UNCHANGED",
"userInteraction": "NONE",
"vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
"version": "3.1"
},
"exploitabilityScore": 1.8,
"impactScore": 5.9,
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"type": "Secondary"
}
]
},
"published": "2026-09-24T17:17:09.930",
"references": [
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/3051cd060fa496df42954291fa2306ed2eab4ecc"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/c4b478bc50b7ca9865e237909941253a0f7111a2"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/f09edffba97d37b1fdff5f818a9a45f8a98ac171"
}
],
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"vulnStatus": "Received"
}
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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
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