{"cve":"CVE-2026-93287","nvd":{"published":"2026-09-24T17:17:09.930","modified":"2026-10-03T11:17:47.247","status":"Received","description":"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->block[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->block[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->block[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  <TASK>\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  </TASK>\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 '__u8 [34]'\n Call Trace:\n  <TASK>\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  </TASK>\n\nBoth traces reproduced on v7.0-rc6+i2c/for-current with KASAN+UBSAN.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","score":7.8},"cwes":[],"references":["https://git.kernel.org/stable/c/3051cd060fa496df42954291fa2306ed2eab4ecc","https://git.kernel.org/stable/c/356875e33f2c6d2061a02c9dec1a1e639d265a55","https://git.kernel.org/stable/c/72ca5e0b8b7a62615758f8871c34d61616c2dc8b","https://git.kernel.org/stable/c/856dffcc097b3d8ed45a643ebda07cb92968cb33","https://git.kernel.org/stable/c/c4b478bc50b7ca9865e237909941253a0f7111a2"],"products":[],"source":"nvd","synced_at":"2026-10-19T22:56:02.509636177+00:00"},"epss":{"cve":"CVE-2026-93287","score":0.00129,"percentile":0.0254,"date":"2026-10-25"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}