CVE-2023-4004

What it actually does

Use-after-free in Linux kernel netfilter nft_pipapo_remove when an element lacks NFT_SET_EXT_KEY_END, enabling local memory corruption that can lead to kernel crash or privilege escalation.

Why it matters to the business

Linux systems may experience unexpected crashes disrupting operations or allow local attackers to gain full system control, risking data exposure and unauthorized access across server and endpoint fleets.

How an attack unfolds

A local attacker with low-privileged access crafts netfilter/nftables operations that invoke nft_pipapo_remove on an element missing the required key-end extension, triggering the use-after-free to corrupt kernel memory and either panic the system or redirect execution for privilege escalation.

How to fix it

Upgrade the Linux kernel to the version containing commit 3602dbc57b556eff2456715301d35a1ef8964bba or later; rebuild and deploy updated kernels across all affected systems, then reboot to activate the fix.

How to confirm the fix worked

Confirm the running kernel includes commit 3602dbc57b556eff2456715301d35a1ef8964bba via git log or version strings; test nftables operations that previously triggered the flaw to verify stability and absence of crashes.

Typical attack path

1. Obtain local shell access on an affected Linux system
2. Load or interact with nftables/netfilter to prepare sets
3. Trigger nft_pipapo_remove on an element lacking NFT_SET_EXT_KEY_END
4. Leverage resulting memory corruption for DoS or code execution to escalate privileges

How to detect it

Review kernel logs for oops or panic messages referencing nft_pipapo_remove or netfilter use-after-free conditions; correlate with unusual nftables rule manipulations by local users.

What your security team should do

• Immediately prioritize kernel updates containing the referenced commit on all Linux deployments
• Restrict untrusted local user access to nftables/netfilter interfaces until patches are applied
• Monitor for kernel oops or panic reports involving netfilter functions
• Schedule staged rollouts and validate stability in test environments before broad deployment