CVE-2025-71118: 
Linux Kernel vulnerability analysis and mitigation

CVE-2025-71118 is a NULL pointer dereference vulnerability in the Linux kernel's ACPICA namespace walking functionality. It was published on January 14, 2026, and affects a wide range of Linux kernel versions from 2.6.12 through 6.19-rc releases, including specific vulnerable ranges: prior to 5.10.248, 5.11.x–5.15.x (prior to 5.15.198), 5.16.x–6.1.x (prior to 6.1.160), 6.2.x–6.6.x (prior to 6.6.120), 6.7.x–6.12.x (prior to 6.12.64), and 6.13.x–6.18.x (prior to 6.18.3). Microsoft Azure Linux (azl3_kernel_6.6.119.3-3) is also affected. The vulnerability carries a CVSS v3.1 base score of 5.5 (Medium) (Feedly, kernel.org patches).

The root cause is a NULL pointer dereference (CWE-476) in the acpi_ns_get_next_node() function within the ACPICA namespace walking code. A prior fix (commit 0c9992315e73) addressed the case where both start_node and acpi_gbl_root_node are NULL, but failed to guard against the case where only start_node is NULL — the check was incorrectly placed inside a conditional block. When the kernel processes a malformed ACPI DSDT (Differentiated System Description Table) during boot, start_node can be NULL, causing an unconditional dereference of parent_node and a kernel panic. The fix moves the NULL check for start_node outside the conditional block to ensure it is always evaluated. This was confirmed to trigger on Honor Magicbook 14 Pro systems with BIOS 1.13 (05/08/2025) carrying a malformed DSDT table (Feedly).

Successful triggering of this vulnerability results in a kernel panic, causing a complete denial of service (DoS) by crashing the affected system. There is no confidentiality or integrity impact — the vulnerability is limited to availability. The attack requires local access with low privileges and no user interaction, and is most likely to manifest on hardware with a malformed ACPI DSDT table (e.g., Honor Magicbook 14 Pro with BIOS 1.13). Lateral movement or data exfiltration are not applicable given the DoS-only nature of the flaw (Feedly).

• Logs: Kernel panic messages referencing acpi_ns_get_next_node() or ACPICA namespace walking in /var/log/kern.log or dmesg output; NULL pointer dereference oops traces in system logs during boot.
• System Behavior: Unexpected system crashes or reboots during the ACPI initialization phase at boot time, particularly on systems with non-standard or vendor-specific BIOS/DSDT tables.
• Hardware Indicators: Systems with DMI string HONOR FMB-P/FMB-P-PCB and BIOS version 1.13 (05/08/2025) are confirmed affected hardware configurations.

Update to a patched Linux kernel version as soon as possible based on your distribution's maintenance stream. Fixed versions include: 5.10.248, 5.15.198, 6.1.160, 6.6.120, 6.12.64, and 6.18.3. Patch commits are available at git.kernel.org (e.g., 0d8bb08, 1bc3429, 7f9b951, 9d6c58d, b84edef, ecb2962, f91dad0). Azure Linux users running azl3_kernel_6.6.119.3-3 should update to a patched azl3_kernel package. After applying the patch, a system reboot is required to activate the fix. For systems that cannot be immediately patched, monitor for unexpected kernel panics during boot and verify BIOS/firmware integrity, particularly on Honor Magicbook hardware (Feedly, kernel.org patches).