CVE-2023-6817

What it actually does

Use-after-free in nft_pipapo_walk due to failure to skip inactive PIPAPO elements during set walks, enabling double deactivation and arbitrary kernel memory access for local privilege escalation.

Why it matters to the business

Local attackers can escalate to root on affected Linux systems, leading to full host compromise, data theft, or persistence; high prevalence in Linux environments increases exposure for servers and endpoints.

How an attack unfolds

An attacker with a local account loads malicious nftables rules that trigger repeated set walks on inactive elements, causing use-after-free and kernel code execution to gain root privileges.

How to fix it

Upgrade the Linux kernel to include commit 317eb9685095678f2c9f5a8189de698c5354316a or later; apply distribution-specific security updates that backport the fix; rebuild and reboot affected systems.

How to confirm the fix worked

Verify kernel source contains commit 317eb9685095678f2c9f5a8189de698c5354316a; confirm running kernel version matches or exceeds patched release from vendor; test nftables operations for absence of crashes or unexpected behavior.

Typical attack path

1. Obtain local user access on target Linux system
2. Craft and load nftables configuration exercising PIPAPO sets with inactive elements
3. Trigger nft_pipapo_walk via netfilter operations to induce double deactivation
4. Exploit resulting use-after-free for kernel memory corruption and privilege escalation
5. Execute payload with elevated privileges

How to detect it

Review kernel audit logs and dmesg for use-after-free warnings or crashes involving nf_tables; inspect nftables rule sets for unusual PIPAPO configurations; correlate with process execution of nft or iptables commands by non-admin users.

What your security team should do

• Apply kernel updates containing commit 317eb9685095678f2c9f5a8189de698c5354316a immediately on all Linux hosts
• Restrict unprivileged nftables access via capabilities or SELinux/AppArmor policies until patched
• Monitor for local privilege escalation attempts in system audit logs
• Prioritize patching on internet-facing or multi-tenant systems given widespread Linux kernel usage