CVE-2025-21689: Linux Kernel

Medium severity, CVSS 5.5. EPSS: 0.2% chance of exploitation in the next 30 days.

In the Linux kernel, the following vulnerability has been resolved: USB: serial: quatech2: fix null-ptr-deref in qt2_process_read_urb() This patch addresses a null-ptr-deref in qt2_process_read_urb() due to an incorrect bounds check in the following: if (newport > serial->num_ports) { dev_err(&port->dev, "%s - port change to invalid port: %i\n", __func__, newport); break; } The condition doesn't account for the valid range of the serial->port buffer, which is from 0 to serial->num_ports - 1. When newport is equal to serial->num_ports, the assignment of "port" in the following code is out-of-bounds and NULL: serial_priv->current_port = newport; port = serial->port[serial_priv->current_port]; The fix checks if newport is greater than or equal to serial->num_ports indicating it is out-of-bounds.

Affected products

• Linux Linux Kernel: from 3.5, before 5.4.290 (fixed in 5.4.290); from 5.5, before 5.10.234 (fixed in 5.10.234); from 5.11, before 5.15.178 (fixed in 5.15.178); from 5.16, before 6.1.128 (fixed in 6.1.128); from 6.2, before 6.6.75 (fixed in 6.6.75); from 6.7, before 6.12.12 (fixed in 6.12.12); …

Published 2025-02-10. Last modified 2026-06-17.