CVE-2023-42754

What it actually does

NULL pointer dereference in the Linux kernel IPv4 stack when an skb lacking a device association reaches __ip_options_compile after IPVS re-routing, resulting in a kernel panic.

Why it matters to the business

Local denial of service on Linux systems that use IPVS, requiring administrative network privileges; high prevalence in server and container environments increases operational disruption risk for workloads relying on the kernel's networking stack.

How an attack unfolds

An attacker with CAP_NET_ADMIN privileges crafts network traffic or uses ipvs configuration to trigger skb re-routing without a device pointer, causing the NULL dereference and system crash when __ip_options_compile is invoked.

How to fix it

Upgrade the Linux kernel to the fixed commit ffc253263a1375a65fa6c9f62a893e9767fbebfa or later; apply vendor-supplied kernel updates that include this patch.

How to confirm the fix worked

Verify the running kernel contains commit ffc253263a1375a65fa6c9f62a893e9767fbebfa via git log or kernel version strings; test IPVS re-routing scenarios to confirm no crash occurs.

Typical attack path

1. Obtain CAP_NET_ADMIN capability on a Linux host
2. Configure or manipulate IPVS to force skb re-routing without device association
3. Send or trigger IPv4 packets that reach __ip_options_compile with a NULL skb->dev
4. Trigger kernel panic and system crash

How to detect it

Search kernel logs for oops or panic messages mentioning __ip_options_compile or ipvs skb handling; correlate with IPVS configuration changes or network traffic from privileged processes.

• kernel: BUG: unable to handle kernel NULL pointer dereference
• __ip_options_compile
• ip_vs

What your security team should do

• Prioritize kernel updates on all systems using IPVS within the next patching cycle
• Restrict CAP_NET_ADMIN to trusted processes and users only
• Monitor for kernel oops or panic events related to ip_options_compile
• Review IPVS configurations for unnecessary exposure to untrusted local users