{"id":"DEBIAN-CVE-2026-64191","details":"In the Linux kernel, the following vulnerability has been resolved:  i2c: stub: Reject I2C block transfers with invalid length  The I2C_SMBUS_I2C_BLOCK_DATA case in stub_xfer() uses data-\u003eblock[0] as the transfer length. The existing check only clamps it to avoid overrunning the chip-\u003ewords[256] register array, but does not validate it against I2C_SMBUS_BLOCK_MAX (32), which is the limit of the union i2c_smbus_data.block buffer (34 bytes total). The driver is a development/test tool (CONFIG_I2C_STUB=m, not built by default) that must be loaded with a chip_addr= parameter.  A local user with access to /dev/i2c-* can issue an I2C_SMBUS ioctl with I2C_SMBUS_I2C_BLOCK_DATA and data-\u003eblock[0] \u003e 32, causing stub_xfer() to read or write past the end of the union i2c_smbus_data.block buffer:   BUG: KASAN: stack-out-of-bounds in stub_xfer (drivers/i2c/i2c-stub.c:223)  Read of size 1 at addr ffff88800abcfd92 by task exploit/81  Call Trace:   \u003cTASK\u003e   stub_xfer (drivers/i2c/i2c-stub.c:223)   __i2c_smbus_xfer (drivers/i2c/i2c-core-smbus.c:593)   i2c_smbus_xfer (drivers/i2c/i2c-core-smbus.c:536)   i2cdev_ioctl_smbus (drivers/i2c/i2c-dev.c:391)   i2cdev_ioctl (drivers/i2c/i2c-dev.c:478)   __x64_sys_ioctl (fs/ioctl.c:583)   do_syscall_64 (arch/x86/entry/syscall_64.c:94)   entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130)   \u003c/TASK\u003e  The bug exists because i2c-stub implements .smbus_xfer directly, bypassing the I2C_SMBUS_BLOCK_MAX validation in i2c_smbus_xfer_emulated(). The I2C_SMBUS_BLOCK_DATA case in the same function correctly validates against I2C_SMBUS_BLOCK_MAX, but the I2C_SMBUS_I2C_BLOCK_DATA case does not.  Fix by rejecting transfers with data-\u003eblock[0] == 0 or data-\u003eblock[0] \u003e I2C_SMBUS_BLOCK_MAX with -EINVAL, consistent with both the I2C_SMBUS_BLOCK_DATA case in the same function and the I2C_SMBUS_I2C_BLOCK_DATA validation in i2c_smbus_xfer_emulated().","modified":"2026-09-01T16:06:55.467428765Z","published":"2026-07-20T17:18:22.217Z","upstream":["CVE-2026-64191"],"references":[{"type":"ADVISORY","url":"https://security-tracker.debian.org/tracker/CVE-2026-64191"}],"affected":[{"package":{"name":"linux","ecosystem":"Debian:12","purl":"pkg:deb/debian/linux?arch=source&distro=bookworm"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.1.177-1"}]}],"versions":["6.1.106-1","6.1.106-2","6.1.106-3","6.1.112-1","6.1.115-1","6.1.119-1","6.1.123-1","6.1.124-1","6.1.128-1","6.1.129-1","6.1.133-1","6.1.135-1","6.1.137-1","6.1.139-1","6.1.140-1","6.1.147-1","6.1.148-1","6.1.153-1","6.1.158-1","6.1.159-1","6.1.162-1","6.1.164-1","6.1.170-1","6.1.170-2","6.1.170-3","6.1.172-1","6.1.174-1","6.1.176-1","6.1.27-1","6.1.37-1","6.1.38-1","6.1.38-2","6.1.38-2~bpo11+1","6.1.38-3","6.1.38-4","6.1.38-4~bpo11+1","6.1.52-1","6.1.55-1","6.1.55-1~bpo11+1","6.1.64-1","6.1.66-1","6.1.67-1","6.1.69-1","6.1.69-1~bpo11+1","6.1.76-1","6.1.76-1~bpo11+1","6.1.82-1","6.1.85-1","6.1.90-1","6.1.90-1~bpo11+1","6.1.94-1","6.1.94-1~bpo11+1","6.1.98-1","6.1.99-1"],"ecosystem_specific":{"urgency":"not 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