CVE-2023-52923

What it actually does

The vulnerability is a race condition in the nf_tables set backend garbage collection that used an outdated buggy GC API and busy mark approach; async GC could unsafely remove elements visible to lookup paths, leading to inconsistent set state or memory corruption.

Why it matters to the business

Linux-based systems using nftables may experience network filtering instability, crashes, or bypasses under concurrent load; low exploitation probability but high operational impact on servers and network appliances until patched, with broad ecosystem reach across kernel deployments.

How an attack unfolds

Attackers leverage the race by issuing concurrent nftables set operations that trigger async GC while lookups or modifications occur; the old API allowed removal of live elements, enabling state corruption that threat actors in 2024 espionage and financially motivated campaigns have targeted in similar kernel races for privilege escalation.

How to fix it

Upgrade the Linux kernel to the fixed commit cb4d00b563675ba8ff6ef94b077f58d816f68ba3 in the stable repository; rebuild and reboot with the updated kernel image, then validate nftables sets under load.

How to confirm the fix worked

Check kernel git commit or version string for cb4d00b563675ba8ff6ef94b077f58d816f68ba3; run stress tests exercising nftables set creation, lookup, and GC paths to confirm no element removal races occur.

Typical attack path

1. Identify systems running vulnerable Linux kernel versions with nftables enabled
2. Load or manipulate nftables sets to create conditions for garbage collection
3. Trigger concurrent async and sync GC paths via crafted network rules or traffic
4. Exploit the race to corrupt set elements or bypass the _DEAD bit protection
5. Escalate to kernel-level access or cause denial of service

How to detect it

Review kernel logs and dmesg for nf_tables GC transaction errors, aborted work items, or set element inconsistencies; correlate with process activity involving nft or network configuration changes.

What your security team should do

• Prioritize kernel updates on all internet-facing and high-traffic Linux systems within the CISA-style remediation window
• Audit nftables configurations for heavy set usage that could trigger GC races
• Enable kernel crash and audit logging for nf_tables events
• Test patches in staging before broad deployment due to kernel update risk