CVE-2015-8812

What it actually does

Use-after-free in the cxgb3 InfiniBand driver (iwch_cm.c) caused by failure to correctly identify error conditions on incoming packets, enabling remote attackers to corrupt kernel memory for arbitrary code execution or denial of service.

Why it matters to the business

Remote attackers can crash affected Linux systems or gain full control, resulting in unplanned downtime, potential data exposure, and loss of availability for workloads running on unpatched kernels; older systems without vendor backports face elevated urgency.

How an attack unfolds

An attacker sends specially crafted network packets targeting the cxgb3 driver; the driver mishandles an error path, leaving a dangling pointer that is later dereferenced, allowing the attacker to control kernel execution flow for code execution or crash.

How to fix it

Upgrade the Linux kernel to version 4.5 or later; apply vendor-supplied backports for supported distributions; disable the cxgb3 module if InfiniBand hardware is not required.

How to confirm the fix worked

Confirm running kernel is 4.5 or newer via uname -r; verify the cxgb3 module is either removed or built from a patched source tree; test that crafted packets no longer trigger the vulnerable code path in a lab environment.

Typical attack path

1. Identify systems exposing cxgb3 InfiniBand interfaces or reachable via IP
2. Transmit crafted packets that trigger the error-handling flaw in iwch_cm.c
3. Leverage the resulting use-after-free to corrupt kernel structures
4. Escalate to arbitrary code execution or trigger denial of service

How to detect it

Review kernel logs (dmesg, /var/log/kern.log) for cxgb3 oops or use-after-free warnings; inspect network captures for unusual traffic patterns to the InfiniBand port; correlate with system crashes on affected hosts.

What your security team should do

• Prioritize kernel upgrades on all affected systems within the next maintenance window
• Inventory systems using cxgb3 hardware or the cxgb3 module
• Apply network segmentation or firewall rules to limit exposure of InfiniBand ports
• Monitor kernel logs and network traffic for anomalous cxgb3-related crashes