CVE-2025-21689

/// Technical description

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.

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References