CVE-2026-23472
MediumCVSS 5.5Exploitation Probability (EPSS)
Low risk2th percentile - higher than 2% of all known CVEs
Summary
In the Linux kernel, a vulnerability in the serial core driver causes an infinite loop in handle_tx() for PORT_UNKNOWN ports. The uart_write_room() function returns a value greater than zero while uart_write() returns 0 when the transmit buffer (xmit_buf) is uninitialized, leading to a system hang.
Risk Assessment
An attacker could exploit this inconsistency to cause a denial of service (system hang) by connecting a misconfigured serial port, disrupting system availability.
Recommendation
Immediately update the Linux kernel to a version containing the fix that synchronizes uart_write_room() behavior with uart_write() for PORT_UNKNOWN ports.
Original NVD description (English source)
In the Linux kernel, the following vulnerability has been resolved: serial: core: fix infinite loop in handle_tx() for PORT_UNKNOWN uart_write_room() and uart_write() behave inconsistently when xmit_buf is NULL (which happens for PORT_UNKNOWN ports that were never properly initialized): - uart_write_room() returns kfifo_avail() which can be > 0 - uart_write() checks xmit_buf and returns 0 if NULL This inconsistency causes an infinite loop in drivers that rely on tty_write_room() to determine if they can write: while (tty_write_room(tty) > 0) { written = tty->ops->write(...); // written is always 0, loop never exits } For example, caif_serial's handle_tx() enters an infinite loop when used with PORT_UNKNOWN serial ports, causing system hangs. Fix by making uart_write_room() also check xmit_buf and return 0 if it's NULL, consistent with uart_write(). Reproducer: https://gist.github.com/mrpre/d9a694cc0e19828ee3bc3b37983fde13