CVE-2025-38265

What it actually does

NULL pointer dereference in serial_base_ctrl_add during jsm_uart_port_init because no device was set before calling into serial_core_register_port, triggering kernel oops on PCI probe of affected serial hardware.

Why it matters to the business

Kernel crashes and system instability on hosts using Digi Neo PCIe serial cards, leading to unplanned downtime and reboots; low urgency given absent KEV listing, low EPSS, and no confirmed ransomware or targeted actor use despite 474 days since publication.

How an attack unfolds

An attacker with local access loads the jsm module or triggers PCI device enumeration for compatible hardware, causing the uninitialized device pointer to dereference during driver probe and resulting in a kernel panic; no specific threat actor campaigns or public exploits are associated with this issue.

How to fix it

Upgrade linux-lts (Alpaquita:stream) to 6.6.58-r0, linux-lts (Alpaquita:23) to 6.1.62-r0, or apply mainline commit 3258d7ff8ebfa451426662b23e8f2b51b129afe1; blacklist the jsm module on systems without the hardware as a temporary mitigation.

How to confirm the fix worked

Confirm updated kernel version boots without oops on Digi Neo PCIe hardware, verify serial_base_ctrl_add no longer receives a NULL device pointer, and retest module probe and port registration paths.

Typical attack path

1. Obtain local access or ability to load kernel modules
2. Insert or enumerate affected Digi Neo PCIe hardware
3. Trigger jsm_probe_one and jsm_uart_port_init paths
4. Induce NULL dereference in serial_base_ctrl_add leading to oops

How to detect it

Search kernel logs and dmesg for 'BUG: kernel NULL pointer dereference' combined with 'serial_base_ctrl_add' or 'jsm_uart_port_init' and 'jsm_probe_one' around crash timestamps; monitor for udev-worker processes triggering PCI probes of serial devices.

What your security team should do

• Apply the listed kernel updates on all affected distributions within standard patch windows
• Audit systems for presence of the jsm driver and disable via modprobe blacklist if hardware is absent
• Incorporate kernel oops monitoring for serial_base_ctrl_add and jsm symbols into existing crash detection