CVE-2025-21689: USB: serial: quatech2: fix null-ptr-deref in qt2_process_read_urb()

Severity: medium (CVSS 5.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2025-02-10 · updated 2026-06-17
Weakness: CWE-476

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.

Affected products

Linux kernel: from 3.5 before 5.4.290; from 5.5 before 5.10.234; from 5.11 before 5.15.178; from 5.16 before 6.1.128; from 6.2 before 6.6.75; from 6.7 before 6.12.12 — fixed in 5.10.234, 5.15.178, 5.4.290, 6.1.128, 6.12.12, 6.6.75

How to fix

Upgrade to a fixed version: Linux kernel 5.10.234, 5.15.178, 5.4.290, 6.1.128. Check the vendor advisory for mitigations.

References

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