CVE-2023-5197

What it actually does

Use-after-free in netfilter nf_tables triggered by concurrent add/remove of rules from chain bindings in a single transaction, enabling local privilege escalation.

Why it matters to the business

Local attackers on affected Linux systems can elevate privileges to root, risking full host compromise, data theft, or persistence; the issue affects a widely deployed kernel component but carries low exploit likelihood and has no ransomware or KEV association despite being public for over three years.

How an attack unfolds

An attacker with a local shell crafts a netfilter transaction that simultaneously adds and removes rules bound to the same chain; the resulting use-after-free object is then manipulated via heap spraying or other memory corruption primitives to overwrite function pointers or credentials, yielding root access.

How to fix it

Upgrade the Linux kernel to a version containing commit f15f29fd4779be8a418b66e9d52979bb6d6c2325 or later; rebuild and reboot with the patched kernel; where live patching is available apply the vendor's hotfix; otherwise schedule maintenance windows for full kernel replacement.

How to confirm the fix worked

Verify the running kernel commit or version string contains f15f29fd4779be8a418b66e9d52979bb6d6c2325; recompile a test module that exercises the transaction path and confirm no crash or privilege gain occurs; monitor for absence of the vulnerable code path in /proc/kallsyms or kernel debug symbols.

Typical attack path

1. Obtain local unprivileged shell on target Linux host
2. Load or ensure nf_tables module is active
3. Issue a single nft transaction containing add and delete operations on chain-bound rules
4. Trigger the use-after-free and perform memory grooming to control freed object
5. Execute privilege-escalation payload to obtain root

How to detect it

Review system audit logs for unusual nftables transactions or repeated module loads; inspect kernel crash dumps or dmesg for use-after-free signatures in nf_tables; correlate with authentication events showing sudden privilege changes.

What your security team should do

• Prioritize kernel updates on internet-facing or multi-tenant systems within normal patch cycles
• Enable kernel lockdown or module signing to raise the bar for local exploitation
• Audit nftables usage and restrict unprivileged users from loading netfilter modules via SELinux or AppArmor
• Include the fixed commit hash in vulnerability scanning signatures for ongoing compliance checks