CVE-2024-43836

What it actually does

Possible null pointer dereference in Linux kernel ethtool PSE-PD handling when a PSE device supports both C33 and PoDL but only one netlink attribute is provided in the configuration request.

Why it matters to the business

Local users can trigger kernel crashes or denial of service on systems using PSE network hardware, leading to unplanned downtime and potential loss of network connectivity for dependent services.

How an attack unfolds

An attacker with local access crafts a netlink ethtool message targeting PSE configuration that omits one of the required attributes for dual-capability PSE devices; the missing validation path before the fix allows dereferencing a null pointer and crashing the kernel.

How to fix it

Update the Linux kernel to a version containing the fix for CVE-2024-43836. Apply the patch that ensures both capability paths are validated after ethnl_set_pse_validate().

How to confirm the fix worked

Confirm the installed kernel contains the commit resolving the null-deref in net/ethtool/pse-pd.c; test PSE configuration with partial attributes on supported hardware to verify no crash occurs.

Typical attack path

1. Obtain local user access on a Linux system with PSE-capable network hardware
2. Invoke ethtool or equivalent netlink call to set PSE attributes supplying only one of C33 or PoDL when both are supported
3. Trigger the unhandled null dereference path in the PSE set operation
4. Cause kernel panic or oops resulting in system reboot or hang

How to detect it

Review kernel logs for oops or panic entries referencing ethtool, pse-pd, or null pointer dereference during netlink attribute handling; correlate with ethtool or ip link commands executed by non-root users.

What your security team should do

• Prioritize kernel updates on systems exposing PSE or PoDL network interfaces
• Restrict unprivileged local access where feasible until patched
• Monitor for kernel oops or panic events related to ethtool or netlink PSE operations