In the Linux kernel, the following vulnerability has been resolved: USB: serial: kl5kusb105: fix bulk-out buffer overflow klsi_105_prepare_write_buffer() is called by the generic write path with the bulk-out buffer and its size (bulk_out_size, 64 bytes). It stores a two-byte length header at the start of the buffer and copies the payload from the write fifo starting at buf + KLSI_HDR_LEN, but passes the full buffer size as the number of bytes to copy: count = kfifo_out_locked(&port->write_fifo, buf + KLSI_HDR_LEN, size, &port->lock); When the fifo holds at least size bytes, size bytes are copied starting two bytes into the size-byte buffer, writing KLSI_HDR_LEN bytes past its end. Copy at most size - KLSI_HDR_LEN bytes instead, leaving room for the header as safe_serial already does. Writing bulk_out_size or more bytes to the tty triggers a slab out-of-bounds write, observed with KASAN by emulating the device with dummy_hcd and raw-gadget: BUG: KASAN: slab-out-of-bounds in kfifo_copy_out+0x83/0xc0 Write of size 64 at addr ffff888112c62202 by task python3 kfifo_copy_out klsi_105_prepare_write_buffer [kl5kusb105] usb_serial_generic_write_start [usbserial] Allocated by task 139: usb_serial_probe [usbserial] The buggy address is located 2 bytes inside of allocated 64-byte region The out-of-bounds write no longer occurs with this change applied.

A flaw was found in the Linux kernel's `kl5kusb105` USB serial driver. This buffer overflow vulnerability allows a local attacker to write data beyond the intended memory boundary (if attacker controls USB device or driver, because triggered from the internals of the device). By sending a specially crafted input to the USB serial port, an attacker can trigger an out-of-bounds write, which may lead to memory corruption. The primary consequence of this flaw is a denial of service (DoS), potentially causing system instability or crashes.

A slab out of bounds write in the USB serial kl5kusb105 transmit path occurs because klsi_105_prepare_write_buffer copies up to the full bulk out buffer size into dest plus KLSI_HDR_LEN, leaving no room for the two byte header. A local user or process that can write bulk_out_size or more bytes to the matching tty device can overflow the 64 byte bulk out buffer by KLSI_HDR_LEN bytes and corrupt adjacent slab memory. To mitigate this issue, prevent module kl5kusb105 from being loaded. Please see https://access.redhat.com/solutions/41278 for how to blacklist a kernel module to prevent it from loading automatically. Red Hat Enterprise Linux 10 Fix deferred kernel Red Hat Enterprise Linux 6 Not affected kernel Red Hat Enterprise Linux 7 Fix deferred kernel Red Hat Enterprise Linux 7 Fix deferred kernel-rt Red Hat Enterprise Linux 8 Fix deferred kernel Red Hat Enterprise Linux 8 Fix deferred kernel-rt Red Hat Enterprise Linux 9 Fix deferred kernel Red Hat Enterprise Linux 9 Fix deferred kernel-rt https://www.cve.org/CVERecord?id=CVE-2026-53194 https://nvd.nist.gov/vuln/detail/CVE-2026-53194 https://lore.kernel.org/linux-cve-announce/2026062558-CVE-2026-53194-8cb6@gregkh/T