CVE-2026-23472: Linux Kernel

Medium severity, CVSS 5.5. EPSS: 0.1% chance of exploitation in the next 30 days.

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

Affected products

• Linux Linux Kernel: from 2.6.12.1, before 6.18.20 (fixed in 6.18.20); from 6.19, before 6.19.10 (fixed in 6.19.10); version 2.6.12 only; version 7.0 only

Published 2026-04-03. Last modified 2026-07-20.