CVE-2026-53194
HighCVSS 7.8Exploitation Probability (EPSS)
Low risk4th percentile - higher than 4% of all known CVEs
Summary
In the Linux kernel's kl5kusb105 USB serial driver, a bulk-out buffer overflow vulnerability was found. The klsi_105_prepare_write_buffer() function copies data from the fifo into a 64-byte buffer without accounting for the two-byte header, causing an out-of-bounds write.
Risk Assessment
An attacker could exploit this vulnerability to write beyond the buffer boundaries, potentially causing a system crash or kernel privilege escalation.
Recommendation
Immediately update the Linux kernel to a version containing the fix that limits copying to size - KLSI_HDR_LEN bytes.
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Original NVD description (English source)
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.